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Debugger
bull A debugger is a program execution platform that allows ndash pausing program execution at specific pointsndash inspecting the values of program variablesndash modifying the values of program variablesndash evaluating arbitrary expressionsndash calling arbitrary routines
bull Debuggers allowndash Controlled stepping through programndash Runtime examination of variablesndash Interactive analysis of programndash No recompile needed each time a possible
bug ruled out
ndash A breakpoint is a pseudo instruction that the user insert at any place into the program at debug time
ndash execution is controlled by the debugger and the debugger will interpret the breakpoints
ndash When execution crosses a breakpoint the debugger will pause program execution
ndash The user can thenbull inspect variablesbull set or clear breakpointsbull continue execution
bull Debugging system provide functions such asndash Tracing
bull Used to track the flow of execution logic amp data modifications
bull Control flow can be traced at different levels Ie procedure branch individual instructionhellip
ndash Trace backbull Show the path by which the current statement was reachedbull Shows which statements have modified a given variable or
parameterndash Program display capability
bull Display the program being debugged complete with statement numbers
bull Software tools to assist the programmer in debugging arendash Debug monitors
bull Provides debugging support for a program by providing information of errors
ndash Source code control systems bull Helps to keep track of the modifications in the
source code
bull Debuggingndash It is the process of isolating amp correcting the causes
of the known errors in a program ndash Debug monitors provides the following facilities for
debugging1 Setting break points in the program2 Initiating a debug conversation when control reaches a
break point3 Displaying values of variables4 Assigning new values to variables5 Testing user defined programs
Steps in Debugging1 User compiles the program under Debug option Compiler
produces1 Compiled code file2 Debug information file
2 User activates the debug monitor amp indicates the name of program to be debugged
3 Debug monitor opens1 Compiled code2 Debug information file of the program
4 User specifies his debug requirements with1 List of break points2 Action to be performed at break points
5 Debug monitor builds a table containing1 Statement number2 Debug action
Steps 4 amp 5 are repeated until the end of the debug session6 Program executes up to a break point and then a software
interrupt is generated amp control is given to the debug monitor then consults debug table and performs the debug actions specified for the break point
7 Control returns to the program
bull Debugger usage modesbull Postmortem analysisbull Program understandingbull Hypothesis testing
Postmortem analysis bull When a program that is run in a debugger crashes
ndash debugger is used to understand the reason for the crashndash This analysis is done after the factndash (post mortem after death)
bull It is based on analyzingndash which calls in the program produced the call nesting that was
active at the time of the crashndash the variables in these active calls
bull Advantagendash Postmortem analysis is simple and possibly quick
bull Disadvantagendash One cannot analyze how the program arrived at the program
state that produced the crash
Program understanding
bull A debugger helps understanding code one does know wellndash Choose simple program inputs firstndash Single-step through the programndash Step into methods of interest step over the restndash Inspect variables as requiredndash Use a breakpoint to finish loops you have understood
bull Advantage ndash No thinking errorsndash Computer keeps track of variable values for you
bull Limitationsndash Difficult to apply for non-sequential programs
Hypothesis testing bull A debugger helps gathering information about
specific aspects of a program without modifying the program
ndash 1048707No need to insert analysis code recompile redeploy
bull Kinds of informationndash 1048707Program state at a certain point during executionndash 1048707Validating specific expected events
bull their occurrencebull their orderbull their frequency
ndash 1048707Catching specific impossible (unexpected) events
Editors
bull A text editor is a type of program used for editing plain text files Often provided with operating systems
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull A debugger is a program execution platform that allows ndash pausing program execution at specific pointsndash inspecting the values of program variablesndash modifying the values of program variablesndash evaluating arbitrary expressionsndash calling arbitrary routines
bull Debuggers allowndash Controlled stepping through programndash Runtime examination of variablesndash Interactive analysis of programndash No recompile needed each time a possible
bug ruled out
ndash A breakpoint is a pseudo instruction that the user insert at any place into the program at debug time
ndash execution is controlled by the debugger and the debugger will interpret the breakpoints
ndash When execution crosses a breakpoint the debugger will pause program execution
ndash The user can thenbull inspect variablesbull set or clear breakpointsbull continue execution
bull Debugging system provide functions such asndash Tracing
bull Used to track the flow of execution logic amp data modifications
bull Control flow can be traced at different levels Ie procedure branch individual instructionhellip
ndash Trace backbull Show the path by which the current statement was reachedbull Shows which statements have modified a given variable or
parameterndash Program display capability
bull Display the program being debugged complete with statement numbers
bull Software tools to assist the programmer in debugging arendash Debug monitors
bull Provides debugging support for a program by providing information of errors
ndash Source code control systems bull Helps to keep track of the modifications in the
source code
bull Debuggingndash It is the process of isolating amp correcting the causes
of the known errors in a program ndash Debug monitors provides the following facilities for
debugging1 Setting break points in the program2 Initiating a debug conversation when control reaches a
break point3 Displaying values of variables4 Assigning new values to variables5 Testing user defined programs
Steps in Debugging1 User compiles the program under Debug option Compiler
produces1 Compiled code file2 Debug information file
2 User activates the debug monitor amp indicates the name of program to be debugged
3 Debug monitor opens1 Compiled code2 Debug information file of the program
4 User specifies his debug requirements with1 List of break points2 Action to be performed at break points
5 Debug monitor builds a table containing1 Statement number2 Debug action
Steps 4 amp 5 are repeated until the end of the debug session6 Program executes up to a break point and then a software
interrupt is generated amp control is given to the debug monitor then consults debug table and performs the debug actions specified for the break point
7 Control returns to the program
bull Debugger usage modesbull Postmortem analysisbull Program understandingbull Hypothesis testing
Postmortem analysis bull When a program that is run in a debugger crashes
ndash debugger is used to understand the reason for the crashndash This analysis is done after the factndash (post mortem after death)
bull It is based on analyzingndash which calls in the program produced the call nesting that was
active at the time of the crashndash the variables in these active calls
bull Advantagendash Postmortem analysis is simple and possibly quick
bull Disadvantagendash One cannot analyze how the program arrived at the program
state that produced the crash
Program understanding
bull A debugger helps understanding code one does know wellndash Choose simple program inputs firstndash Single-step through the programndash Step into methods of interest step over the restndash Inspect variables as requiredndash Use a breakpoint to finish loops you have understood
bull Advantage ndash No thinking errorsndash Computer keeps track of variable values for you
bull Limitationsndash Difficult to apply for non-sequential programs
Hypothesis testing bull A debugger helps gathering information about
specific aspects of a program without modifying the program
ndash 1048707No need to insert analysis code recompile redeploy
bull Kinds of informationndash 1048707Program state at a certain point during executionndash 1048707Validating specific expected events
bull their occurrencebull their orderbull their frequency
ndash 1048707Catching specific impossible (unexpected) events
Editors
bull A text editor is a type of program used for editing plain text files Often provided with operating systems
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull Debuggers allowndash Controlled stepping through programndash Runtime examination of variablesndash Interactive analysis of programndash No recompile needed each time a possible
bug ruled out
ndash A breakpoint is a pseudo instruction that the user insert at any place into the program at debug time
ndash execution is controlled by the debugger and the debugger will interpret the breakpoints
ndash When execution crosses a breakpoint the debugger will pause program execution
ndash The user can thenbull inspect variablesbull set or clear breakpointsbull continue execution
bull Debugging system provide functions such asndash Tracing
bull Used to track the flow of execution logic amp data modifications
bull Control flow can be traced at different levels Ie procedure branch individual instructionhellip
ndash Trace backbull Show the path by which the current statement was reachedbull Shows which statements have modified a given variable or
parameterndash Program display capability
bull Display the program being debugged complete with statement numbers
bull Software tools to assist the programmer in debugging arendash Debug monitors
bull Provides debugging support for a program by providing information of errors
ndash Source code control systems bull Helps to keep track of the modifications in the
source code
bull Debuggingndash It is the process of isolating amp correcting the causes
of the known errors in a program ndash Debug monitors provides the following facilities for
debugging1 Setting break points in the program2 Initiating a debug conversation when control reaches a
break point3 Displaying values of variables4 Assigning new values to variables5 Testing user defined programs
Steps in Debugging1 User compiles the program under Debug option Compiler
produces1 Compiled code file2 Debug information file
2 User activates the debug monitor amp indicates the name of program to be debugged
3 Debug monitor opens1 Compiled code2 Debug information file of the program
4 User specifies his debug requirements with1 List of break points2 Action to be performed at break points
5 Debug monitor builds a table containing1 Statement number2 Debug action
Steps 4 amp 5 are repeated until the end of the debug session6 Program executes up to a break point and then a software
interrupt is generated amp control is given to the debug monitor then consults debug table and performs the debug actions specified for the break point
7 Control returns to the program
bull Debugger usage modesbull Postmortem analysisbull Program understandingbull Hypothesis testing
Postmortem analysis bull When a program that is run in a debugger crashes
ndash debugger is used to understand the reason for the crashndash This analysis is done after the factndash (post mortem after death)
bull It is based on analyzingndash which calls in the program produced the call nesting that was
active at the time of the crashndash the variables in these active calls
bull Advantagendash Postmortem analysis is simple and possibly quick
bull Disadvantagendash One cannot analyze how the program arrived at the program
state that produced the crash
Program understanding
bull A debugger helps understanding code one does know wellndash Choose simple program inputs firstndash Single-step through the programndash Step into methods of interest step over the restndash Inspect variables as requiredndash Use a breakpoint to finish loops you have understood
bull Advantage ndash No thinking errorsndash Computer keeps track of variable values for you
bull Limitationsndash Difficult to apply for non-sequential programs
Hypothesis testing bull A debugger helps gathering information about
specific aspects of a program without modifying the program
ndash 1048707No need to insert analysis code recompile redeploy
bull Kinds of informationndash 1048707Program state at a certain point during executionndash 1048707Validating specific expected events
bull their occurrencebull their orderbull their frequency
ndash 1048707Catching specific impossible (unexpected) events
Editors
bull A text editor is a type of program used for editing plain text files Often provided with operating systems
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
ndash A breakpoint is a pseudo instruction that the user insert at any place into the program at debug time
ndash execution is controlled by the debugger and the debugger will interpret the breakpoints
ndash When execution crosses a breakpoint the debugger will pause program execution
ndash The user can thenbull inspect variablesbull set or clear breakpointsbull continue execution
bull Debugging system provide functions such asndash Tracing
bull Used to track the flow of execution logic amp data modifications
bull Control flow can be traced at different levels Ie procedure branch individual instructionhellip
ndash Trace backbull Show the path by which the current statement was reachedbull Shows which statements have modified a given variable or
parameterndash Program display capability
bull Display the program being debugged complete with statement numbers
bull Software tools to assist the programmer in debugging arendash Debug monitors
bull Provides debugging support for a program by providing information of errors
ndash Source code control systems bull Helps to keep track of the modifications in the
source code
bull Debuggingndash It is the process of isolating amp correcting the causes
of the known errors in a program ndash Debug monitors provides the following facilities for
debugging1 Setting break points in the program2 Initiating a debug conversation when control reaches a
break point3 Displaying values of variables4 Assigning new values to variables5 Testing user defined programs
Steps in Debugging1 User compiles the program under Debug option Compiler
produces1 Compiled code file2 Debug information file
2 User activates the debug monitor amp indicates the name of program to be debugged
3 Debug monitor opens1 Compiled code2 Debug information file of the program
4 User specifies his debug requirements with1 List of break points2 Action to be performed at break points
5 Debug monitor builds a table containing1 Statement number2 Debug action
Steps 4 amp 5 are repeated until the end of the debug session6 Program executes up to a break point and then a software
interrupt is generated amp control is given to the debug monitor then consults debug table and performs the debug actions specified for the break point
7 Control returns to the program
bull Debugger usage modesbull Postmortem analysisbull Program understandingbull Hypothesis testing
Postmortem analysis bull When a program that is run in a debugger crashes
ndash debugger is used to understand the reason for the crashndash This analysis is done after the factndash (post mortem after death)
bull It is based on analyzingndash which calls in the program produced the call nesting that was
active at the time of the crashndash the variables in these active calls
bull Advantagendash Postmortem analysis is simple and possibly quick
bull Disadvantagendash One cannot analyze how the program arrived at the program
state that produced the crash
Program understanding
bull A debugger helps understanding code one does know wellndash Choose simple program inputs firstndash Single-step through the programndash Step into methods of interest step over the restndash Inspect variables as requiredndash Use a breakpoint to finish loops you have understood
bull Advantage ndash No thinking errorsndash Computer keeps track of variable values for you
bull Limitationsndash Difficult to apply for non-sequential programs
Hypothesis testing bull A debugger helps gathering information about
specific aspects of a program without modifying the program
ndash 1048707No need to insert analysis code recompile redeploy
bull Kinds of informationndash 1048707Program state at a certain point during executionndash 1048707Validating specific expected events
bull their occurrencebull their orderbull their frequency
ndash 1048707Catching specific impossible (unexpected) events
Editors
bull A text editor is a type of program used for editing plain text files Often provided with operating systems
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull Debugging system provide functions such asndash Tracing
bull Used to track the flow of execution logic amp data modifications
bull Control flow can be traced at different levels Ie procedure branch individual instructionhellip
ndash Trace backbull Show the path by which the current statement was reachedbull Shows which statements have modified a given variable or
parameterndash Program display capability
bull Display the program being debugged complete with statement numbers
bull Software tools to assist the programmer in debugging arendash Debug monitors
bull Provides debugging support for a program by providing information of errors
ndash Source code control systems bull Helps to keep track of the modifications in the
source code
bull Debuggingndash It is the process of isolating amp correcting the causes
of the known errors in a program ndash Debug monitors provides the following facilities for
debugging1 Setting break points in the program2 Initiating a debug conversation when control reaches a
break point3 Displaying values of variables4 Assigning new values to variables5 Testing user defined programs
Steps in Debugging1 User compiles the program under Debug option Compiler
produces1 Compiled code file2 Debug information file
2 User activates the debug monitor amp indicates the name of program to be debugged
3 Debug monitor opens1 Compiled code2 Debug information file of the program
4 User specifies his debug requirements with1 List of break points2 Action to be performed at break points
5 Debug monitor builds a table containing1 Statement number2 Debug action
Steps 4 amp 5 are repeated until the end of the debug session6 Program executes up to a break point and then a software
interrupt is generated amp control is given to the debug monitor then consults debug table and performs the debug actions specified for the break point
7 Control returns to the program
bull Debugger usage modesbull Postmortem analysisbull Program understandingbull Hypothesis testing
Postmortem analysis bull When a program that is run in a debugger crashes
ndash debugger is used to understand the reason for the crashndash This analysis is done after the factndash (post mortem after death)
bull It is based on analyzingndash which calls in the program produced the call nesting that was
active at the time of the crashndash the variables in these active calls
bull Advantagendash Postmortem analysis is simple and possibly quick
bull Disadvantagendash One cannot analyze how the program arrived at the program
state that produced the crash
Program understanding
bull A debugger helps understanding code one does know wellndash Choose simple program inputs firstndash Single-step through the programndash Step into methods of interest step over the restndash Inspect variables as requiredndash Use a breakpoint to finish loops you have understood
bull Advantage ndash No thinking errorsndash Computer keeps track of variable values for you
bull Limitationsndash Difficult to apply for non-sequential programs
Hypothesis testing bull A debugger helps gathering information about
specific aspects of a program without modifying the program
ndash 1048707No need to insert analysis code recompile redeploy
bull Kinds of informationndash 1048707Program state at a certain point during executionndash 1048707Validating specific expected events
bull their occurrencebull their orderbull their frequency
ndash 1048707Catching specific impossible (unexpected) events
Editors
bull A text editor is a type of program used for editing plain text files Often provided with operating systems
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull Software tools to assist the programmer in debugging arendash Debug monitors
bull Provides debugging support for a program by providing information of errors
ndash Source code control systems bull Helps to keep track of the modifications in the
source code
bull Debuggingndash It is the process of isolating amp correcting the causes
of the known errors in a program ndash Debug monitors provides the following facilities for
debugging1 Setting break points in the program2 Initiating a debug conversation when control reaches a
break point3 Displaying values of variables4 Assigning new values to variables5 Testing user defined programs
Steps in Debugging1 User compiles the program under Debug option Compiler
produces1 Compiled code file2 Debug information file
2 User activates the debug monitor amp indicates the name of program to be debugged
3 Debug monitor opens1 Compiled code2 Debug information file of the program
4 User specifies his debug requirements with1 List of break points2 Action to be performed at break points
5 Debug monitor builds a table containing1 Statement number2 Debug action
Steps 4 amp 5 are repeated until the end of the debug session6 Program executes up to a break point and then a software
interrupt is generated amp control is given to the debug monitor then consults debug table and performs the debug actions specified for the break point
7 Control returns to the program
bull Debugger usage modesbull Postmortem analysisbull Program understandingbull Hypothesis testing
Postmortem analysis bull When a program that is run in a debugger crashes
ndash debugger is used to understand the reason for the crashndash This analysis is done after the factndash (post mortem after death)
bull It is based on analyzingndash which calls in the program produced the call nesting that was
active at the time of the crashndash the variables in these active calls
bull Advantagendash Postmortem analysis is simple and possibly quick
bull Disadvantagendash One cannot analyze how the program arrived at the program
state that produced the crash
Program understanding
bull A debugger helps understanding code one does know wellndash Choose simple program inputs firstndash Single-step through the programndash Step into methods of interest step over the restndash Inspect variables as requiredndash Use a breakpoint to finish loops you have understood
bull Advantage ndash No thinking errorsndash Computer keeps track of variable values for you
bull Limitationsndash Difficult to apply for non-sequential programs
Hypothesis testing bull A debugger helps gathering information about
specific aspects of a program without modifying the program
ndash 1048707No need to insert analysis code recompile redeploy
bull Kinds of informationndash 1048707Program state at a certain point during executionndash 1048707Validating specific expected events
bull their occurrencebull their orderbull their frequency
ndash 1048707Catching specific impossible (unexpected) events
Editors
bull A text editor is a type of program used for editing plain text files Often provided with operating systems
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull Debuggingndash It is the process of isolating amp correcting the causes
of the known errors in a program ndash Debug monitors provides the following facilities for
debugging1 Setting break points in the program2 Initiating a debug conversation when control reaches a
break point3 Displaying values of variables4 Assigning new values to variables5 Testing user defined programs
Steps in Debugging1 User compiles the program under Debug option Compiler
produces1 Compiled code file2 Debug information file
2 User activates the debug monitor amp indicates the name of program to be debugged
3 Debug monitor opens1 Compiled code2 Debug information file of the program
4 User specifies his debug requirements with1 List of break points2 Action to be performed at break points
5 Debug monitor builds a table containing1 Statement number2 Debug action
Steps 4 amp 5 are repeated until the end of the debug session6 Program executes up to a break point and then a software
interrupt is generated amp control is given to the debug monitor then consults debug table and performs the debug actions specified for the break point
7 Control returns to the program
bull Debugger usage modesbull Postmortem analysisbull Program understandingbull Hypothesis testing
Postmortem analysis bull When a program that is run in a debugger crashes
ndash debugger is used to understand the reason for the crashndash This analysis is done after the factndash (post mortem after death)
bull It is based on analyzingndash which calls in the program produced the call nesting that was
active at the time of the crashndash the variables in these active calls
bull Advantagendash Postmortem analysis is simple and possibly quick
bull Disadvantagendash One cannot analyze how the program arrived at the program
state that produced the crash
Program understanding
bull A debugger helps understanding code one does know wellndash Choose simple program inputs firstndash Single-step through the programndash Step into methods of interest step over the restndash Inspect variables as requiredndash Use a breakpoint to finish loops you have understood
bull Advantage ndash No thinking errorsndash Computer keeps track of variable values for you
bull Limitationsndash Difficult to apply for non-sequential programs
Hypothesis testing bull A debugger helps gathering information about
specific aspects of a program without modifying the program
ndash 1048707No need to insert analysis code recompile redeploy
bull Kinds of informationndash 1048707Program state at a certain point during executionndash 1048707Validating specific expected events
bull their occurrencebull their orderbull their frequency
ndash 1048707Catching specific impossible (unexpected) events
Editors
bull A text editor is a type of program used for editing plain text files Often provided with operating systems
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Steps in Debugging1 User compiles the program under Debug option Compiler
produces1 Compiled code file2 Debug information file
2 User activates the debug monitor amp indicates the name of program to be debugged
3 Debug monitor opens1 Compiled code2 Debug information file of the program
4 User specifies his debug requirements with1 List of break points2 Action to be performed at break points
5 Debug monitor builds a table containing1 Statement number2 Debug action
Steps 4 amp 5 are repeated until the end of the debug session6 Program executes up to a break point and then a software
interrupt is generated amp control is given to the debug monitor then consults debug table and performs the debug actions specified for the break point
7 Control returns to the program
bull Debugger usage modesbull Postmortem analysisbull Program understandingbull Hypothesis testing
Postmortem analysis bull When a program that is run in a debugger crashes
ndash debugger is used to understand the reason for the crashndash This analysis is done after the factndash (post mortem after death)
bull It is based on analyzingndash which calls in the program produced the call nesting that was
active at the time of the crashndash the variables in these active calls
bull Advantagendash Postmortem analysis is simple and possibly quick
bull Disadvantagendash One cannot analyze how the program arrived at the program
state that produced the crash
Program understanding
bull A debugger helps understanding code one does know wellndash Choose simple program inputs firstndash Single-step through the programndash Step into methods of interest step over the restndash Inspect variables as requiredndash Use a breakpoint to finish loops you have understood
bull Advantage ndash No thinking errorsndash Computer keeps track of variable values for you
bull Limitationsndash Difficult to apply for non-sequential programs
Hypothesis testing bull A debugger helps gathering information about
specific aspects of a program without modifying the program
ndash 1048707No need to insert analysis code recompile redeploy
bull Kinds of informationndash 1048707Program state at a certain point during executionndash 1048707Validating specific expected events
bull their occurrencebull their orderbull their frequency
ndash 1048707Catching specific impossible (unexpected) events
Editors
bull A text editor is a type of program used for editing plain text files Often provided with operating systems
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull Debugger usage modesbull Postmortem analysisbull Program understandingbull Hypothesis testing
Postmortem analysis bull When a program that is run in a debugger crashes
ndash debugger is used to understand the reason for the crashndash This analysis is done after the factndash (post mortem after death)
bull It is based on analyzingndash which calls in the program produced the call nesting that was
active at the time of the crashndash the variables in these active calls
bull Advantagendash Postmortem analysis is simple and possibly quick
bull Disadvantagendash One cannot analyze how the program arrived at the program
state that produced the crash
Program understanding
bull A debugger helps understanding code one does know wellndash Choose simple program inputs firstndash Single-step through the programndash Step into methods of interest step over the restndash Inspect variables as requiredndash Use a breakpoint to finish loops you have understood
bull Advantage ndash No thinking errorsndash Computer keeps track of variable values for you
bull Limitationsndash Difficult to apply for non-sequential programs
Hypothesis testing bull A debugger helps gathering information about
specific aspects of a program without modifying the program
ndash 1048707No need to insert analysis code recompile redeploy
bull Kinds of informationndash 1048707Program state at a certain point during executionndash 1048707Validating specific expected events
bull their occurrencebull their orderbull their frequency
ndash 1048707Catching specific impossible (unexpected) events
Editors
bull A text editor is a type of program used for editing plain text files Often provided with operating systems
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Postmortem analysis bull When a program that is run in a debugger crashes
ndash debugger is used to understand the reason for the crashndash This analysis is done after the factndash (post mortem after death)
bull It is based on analyzingndash which calls in the program produced the call nesting that was
active at the time of the crashndash the variables in these active calls
bull Advantagendash Postmortem analysis is simple and possibly quick
bull Disadvantagendash One cannot analyze how the program arrived at the program
state that produced the crash
Program understanding
bull A debugger helps understanding code one does know wellndash Choose simple program inputs firstndash Single-step through the programndash Step into methods of interest step over the restndash Inspect variables as requiredndash Use a breakpoint to finish loops you have understood
bull Advantage ndash No thinking errorsndash Computer keeps track of variable values for you
bull Limitationsndash Difficult to apply for non-sequential programs
Hypothesis testing bull A debugger helps gathering information about
specific aspects of a program without modifying the program
ndash 1048707No need to insert analysis code recompile redeploy
bull Kinds of informationndash 1048707Program state at a certain point during executionndash 1048707Validating specific expected events
bull their occurrencebull their orderbull their frequency
ndash 1048707Catching specific impossible (unexpected) events
Editors
bull A text editor is a type of program used for editing plain text files Often provided with operating systems
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Program understanding
bull A debugger helps understanding code one does know wellndash Choose simple program inputs firstndash Single-step through the programndash Step into methods of interest step over the restndash Inspect variables as requiredndash Use a breakpoint to finish loops you have understood
bull Advantage ndash No thinking errorsndash Computer keeps track of variable values for you
bull Limitationsndash Difficult to apply for non-sequential programs
Hypothesis testing bull A debugger helps gathering information about
specific aspects of a program without modifying the program
ndash 1048707No need to insert analysis code recompile redeploy
bull Kinds of informationndash 1048707Program state at a certain point during executionndash 1048707Validating specific expected events
bull their occurrencebull their orderbull their frequency
ndash 1048707Catching specific impossible (unexpected) events
Editors
bull A text editor is a type of program used for editing plain text files Often provided with operating systems
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Hypothesis testing bull A debugger helps gathering information about
specific aspects of a program without modifying the program
ndash 1048707No need to insert analysis code recompile redeploy
bull Kinds of informationndash 1048707Program state at a certain point during executionndash 1048707Validating specific expected events
bull their occurrencebull their orderbull their frequency
ndash 1048707Catching specific impossible (unexpected) events
Editors
bull A text editor is a type of program used for editing plain text files Often provided with operating systems
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Editors
bull A text editor is a type of program used for editing plain text files Often provided with operating systems
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull A text editor is a type of program used for editing plain text files Often provided with operating systems
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Features of text editorsbull DaggerString searching algorithmbull DaggerCut copy and pastebull DaggerText formattingbull DaggerUndo and redobull DaggerData transformationbull DaggerFilteringbull Syntax highlighting
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Types of Editors
bull Line editorsbull Stream editorsbull Screen editorsbull Word processorsbull Structure editors
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Line Editors
ndash Scope of line editors is limited to a line of textndash The line is designated positionally by
specifying the serial number in the textndash Edit characters like end of line is maintained
internallyndash Advantage
bull SimplicityEg-ed is a line editor for the Unix operating system
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull Line Editorbull bull Line editor is one of the simplest type of
editor which uses a buffer to store information
bull bull It operates in command mode User give the command to the editor for any operation Editor will respond this command
bull bull Buffer is in the main memory That is set aside to store the information which is entered from the keyboard
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull Meritsbull 1) Simple for read and writebull 2) Simple in design and implementationbull 3) Command and responses are
interleavedbull Demeritsbull 1) Not user friendlybull 2) Context of the text is not displayedbull 3) Only single line
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Stream Editorsndash Views the entire text as a stream of characters amp
permits edit operation to cross line boundariesndash It support character line amp context oriented editing
commandsndash Current editing context is indicated by the position of
the text pointer called cursorndash Cursor can be used to move across amp within the linesndash Cursor can be moved by using positioning amp search
commands
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Screen Editors
ndash It uses what-you-see- is what-you-get modendash It displays a screen full of text at a timendash User can move the cursor over the screen
position it on a point where the editing process is to be performed
ndash Effect of edit operation can be seen on the screen
ndash Useful while formatting the text to produce printed documents
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Word processors
ndash Document editors with additional features to produce well formatted hard copy output
ndash Featuresbull Commands for moving section of text from one
place to anotherbull Merging of textbull Searching wordsbull Replacing wordsbull Spell checking
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Structure Editors
ndash Incorporates an awareness of the structure of a document
ndash Useful in browsing through a document amp editing it
ndash Structure is specified while creating or modifying the document
ndash Editing requirement is specified using structure
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Editing Processbull Document-editing process is an interactive
user-computer dialogue designed to accomplish 4 tasks
1 Select the part of the target document to be viewed and manipulated
2 Determine how to format this view on-line amp how to display it
3 Specify amp execute operations that modify the target document
4 Update the view appropriately
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull Travellingndash Moving through the editing document to a new
position in the textndash Done explicitly by the userndash It specifies where the area of interest is
bull Editingndash Adding new textndash Modifying the existing textndash Erasing the contentndash Formatting the existing data
bull Viewing amp displaying ndash Viewing amp formatting the text desired for the userndash Abstract viewndash Display component maps this abstract view into the
physical characteristics of the display device being used amp determines where a particular text may appear on user screen
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Editor Structure
Commandlanguageprocessor
Editingcomponent
Travelingcomponent
Viewingcomponent
Displaycomponent
Editingbuffer
Viewingbuffer
EditingFilter
Viewingfilter
Mainmemory
Filesystem
input
Output devices
Paging
routines
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull Command language processorndash It accepts input from the usersrsquos input device amp analyses the
tokens and syntactic structure of the commandsndash It then produce an intermediate representation of the desired
editing operationsndash Interpreter then decodes this intermediate representation
bull Editing managerndash Start of the area to be edited is determined by the current editing
pointer maintained by the editing managerndash Current editing pointer can be set or reset explicitly by the user
with traveling commands such as next paragraph or implicitly as a side effect of the previous edit operation as delete paragraph
bull Traveling managerndash Setting of the current editing and viewing pointersndash Invoked explicitly by the user or implicitly by editing operations
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull Viewing Managerndash Start of the area to be viewed is determined by current viewing
pointerndash It is maintained by viewing manager which is collection of
modules responsible for determining the next viewndash Current viewing pointer can be set or reset explicitly by the user
or implicitly by the system as a result of the previous edit operation
bull Display Managerndash Makes provision for appropriate display of textndash Its function may be combined with viewing manager
bull Viewing Filterndash To update display viewing manager invokes the viewing filterndash It filters the document to generate a new buffer with content for
viewingbull Viewing Buffer
ndash Has the content for viewingndash This content is passed to the viewing manager which produces
the display by mapping the buffers content to a window
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull Editing filterndash Filtering is the process of selection of contiguous
characters beginning from the current positionndash When the user issues an edit command the editing
manager invokes the editing filter This filter filters the document to generate a new buffer with content for editing
ndash As editing is performed editing filter reflects the changes into the internal form amp updates the contents of the viewing buffer inorder to make the changes visible on the screen
ndash Support an undo function by storing a stack of previous views
bull Editing bufferndash Editing filter creates an editing buffer that contains the
portion of document selected by the user for editing
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
A text editor is a type of program used for editing plain text filesOften provided with operating systems
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Line EditorDagger Scope of edit operations is limited to a line of textDaggerbull The line is designated positionally Advantage-SimplicityDisadvantage- Does not display the text in the manner it would appear if
printed
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Stream Editorbull Views the entire text as a stream
of charactersbull This permits edit operations to cross line
boundariesbull Support character line and context
oriented commands based on the current editing context indicated by the position of a text pointer
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull Screen Editor bull DaggerA screen editor uses the what you see is
what you get principle in editor designbull DaggerThe user can move the cursor over the
screen position it at the point where he desires to perform some editing and proceed with the editing directly
bull Advantage-Useful while formatting the text to produce printed documents
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
bull Word ProcessorsBasically document editors with additional
features to produce well formatted hard copy output
bull Essential features of word processors are commands for moving sections of text from one place to another mergingof text and searching and replacement of words Many word processors support a spell check optioneg Wordstar
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Structure EditorsIncorporates an awareness of the structure
of a documentbull DaggerStructure is specified by the user while
creating or modifying the documentbull DaggerEditing requirements are specified using
thestructurebull DaggerA special class of structure editors
called syntax directed editors are used in programming environments
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge
Advantages and Disadvantages Text Editor
bull Simple and places less demands on system
bull Provides greater control over the application
bull Difficult to Visualise output(eg to preview a webpage you have to have a suitable browser)
bull Dependant on programming or text-based commands knowledge