Unit III: Linkers and Loaders and Software

Unit III: Linkers and Loaders and Software

Linkers and Loaders: Basic loaders functions, central loaders scheme, absolute loaders, Subroutine linkers, relocation loader, Direct linking loader, Dynamic linking loader, Design of absolute loaders and direct linking loader, Software tools: Software tools for programdevelopment, editors, debug monitor, programming environment, user interfaces.Software Tools for program DevelopmentSoftware tools are used extensively for program development and user interfaces

EditorDebug monitorProgramming EnvironmentUser Interfaces

EditorEditor is computer program that allows a user to create and revise target documentDocument includes object as computer programs, text, equations, tables, diagrams, lines and photographs.

EditorThe document editing process is an interactive user-computer dialogue1.Select the part to view and manipulate2.To determine the format of and display3.Specify and execute operation4.Update the view appropriately

EditorText editor are of following types1.Line Editors2.Sreen Editors3.Word processors4.Structure EditiorsLine EditorsIt is primitive form of editorUser has to specify line to change textInteraction with the editors is through a set of commands , this makes a editor less user friendlyE.g. vi editor, vim editorScreen EditorsScreen editors enables to modify any text by moving cursor to desired location.This is very useful while formatting the text to produce printed documentE.g. office document.Word processorA word processor recognize word a basic entityIt support spell check optionIt has following options 1.Moving a section of text from one place to another 2.Delecting a section of text 3.Searching a word 4.Merging of text 5.Replacement of word 6.Spell-CheckStructure EditorsA structure editor has awareness of structure of document.A structure is specified by user while creating and modifying the document.E.g. LatTexEditor Structure

Editor StructureEditing module is collection of module deling with editing tasks.Travelling module of editor performs the setting of the current editing and viewing pointersIn viewing module start of the area to be view is determine by current viewing pointerDebug MonitorDebug monitor provides following facilities1.Setting breakpoints in the program2.Initiating a debug conversation3.Displaying values of variables4.Assigning new values to variableDebug MonitorDebugging system provides functions such as tracing and trackback.Tracking used to track the flow of execution logic and data modificationTrackback can show path by which the current statement reachedIn debugging user specifies breakpoints and action to be performedProgramming EnvironmentProgramming environment is an integrated program development environmentIt has following facilities 1.Program creation 2.Editing 3.Execuation 4.Testing and debuggingProgramming EnvironmentProgramming Environment has following components 1. A syntax directed editor 2.Compier ,Interpreter 3.Debug monitor 4.Dialog monitorUser InterfacesA user interface plays an important role in simplifying the interaction of user with applicationUI functioning has two important aspects 1.Issuing Commands 2.Excange of data User Interfaces

User InterfaceThe presentation manger is responsible for managing users screen and for accepting dataThe dialog manager is responsible for interpreting user command and implement themDialog manger is also responsible for error message