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Introducing Computer Introducing Computer Science & AlgorithmsScience & Algorithms
GoalsGoalsBy the end of this lecture you
should …… understand Computer Science
as the study of algorithms… understand the difference
between procedural-type languages and object-oriented languages
… understand the program development cycle
Types of ComputersTypes of Computers
Personal Computer - a computer operated by one person at a time. AKA “Client” computers.
Server – a computer whose resources and processors are shared by multiple users
VB.Net concerns itself mainly with programming for the client computer
Computer use is PervasiveComputer use is PervasiveBanking Air TrafficSpace TravelCommerceMedicinePublic SafetyEducation
Computer ComponentsComputer ComponentsHardware
◦ Physical components of a computer◦ Examples: Mouse, keyboard, RAM, hard drives,
processor, monitorSoftware
◦ Instructions that get the computer to do something◦ Operating Systems & Applications◦ Examples: Windows 2000, Microsoft Excel,
WordPerfect, Netscape, Internet Explorer
What is Computer What is Computer Science?Science?
NOT about coding or hardware or software!
Computer Science is about PROBLEM SOLVING
Computer Science is about DEVELOPING ALGORITHMS to solve complex problems
Computers are merely tools for solving problems!
AlgorithmsAlgorithms
Well-developed, organized approaches to solving complex problems
Test of a good algorithm:◦Does the algorithm solve the stated
problem?◦Is the algorithm well-defined?◦Does the algorithm produce an output?◦Does the algorithm end in a reasonable
length of time?
Developing an AlgorithmDeveloping an Algorithm1. Identify the Inputs
◦ What data do I need?◦ How will I get the data?◦ In what format will the data be?
2. Identify the Processes:◦ How can I manipulate data to produce
meaningful results?
3. Identify Outputs:◦ What outputs do I need to return to the user?◦ What format should the outputs take?
Developing an AlgorithmDeveloping an Algorithm
PROBLEM
INPUT PROCESSES OUTPUT
MODULE MODULE MODULE MODULE MODULE MODULE
4. Develop a HIPO chart
Developing an AlgorithmDeveloping an Algorithm
5. Identify relevant modules◦ How can I break larger problems
into smaller, more manageable pieces?
◦ What inputs do the modules need?◦ What processes need to happen in
the modules?◦ What outputs are produced by the
modules?
ProgramsProgramsSets of instructions that get the
computer to do somethingInstructions are translated,
eventually, to machine language using an interpreter or a compiler
Programs may be a few lines or millions of lines of code
Programming TasksProgramming TasksAll computer programs are written so
they can take data, manipulate and then produce a result.
This process uses three distinct tasks:◦ INPUT – getting data from an external source (the
user, a database, a file, etc.)◦ PROCESSING – actual manipulation of the data◦ OUTPUT – reporting the results of data
manipulation back (using the monitor, writing information to a database, etc.)
Relationships in Relationships in ProgrammingProgrammingProgrammer – The person who
solves a problem by providing a solution through writing instructions (the program) for the computer. (AKA – The developer)
User – Any person who uses a program written by a programmer
Categories of LanguagesCategories of LanguagesMachine Language
◦ Binary digits (bits – 1s and 0s) which are translated to electrical impulses that get the computer to do something
◦ “Native” language of computersAssembly Languages
◦ Group of basic commands which are more like English
◦ Tied to specific processors◦ Still need to be translated to machine language
Categories of LanguagesCategories of LanguagesHigh Level Languages
◦In terms of syntax, very close to human language (mostly English)
◦Lower error rate than writing machine language or assembly language programs
◦Need to be translated to machine language before execution Compilers Interpreters
More on High-Level More on High-Level LanguagesLanguagesOperations common to all HL
languages:◦Sequential Operations – Operations in
which lines of code execute in order, one right after another
◦Conditional Operations – Operations in which execution depends on the outcome of a previous condition (usually evaluated to be TRUE or FALSE)
◦Looping Operations – Operations designed to repeat until a given condition is satisfied.
More on High-Level More on High-Level LanguagesLanguagesProcedural Languages
◦Early high level languages◦Focus on structures◦Examples include QuickBasic, Fortran,
Pascal, Visual Basic (early versions)Object-Oriented languages (OOP)
◦More recent development◦Focus on data, not structures
(Primacy of Data)◦Examples include Java, C#, C++,
Visual Basic.Net
Object Oriented Object Oriented ProgrammingProgrammingObject – Unique programming
entity that has methods, has attributes and can react to events.
Method – Things which an object can do; the “verbs” of objects. In code, usually can be identified by an “action” word -- Hide, Show
Object Oriented Object Oriented ProgrammingProgrammingAttribute – Things which describe
an object; the “adjectives” of objects. In code, usually can be identified by a “descriptive” word – Enabled, BackColor
Events – Forces external to an object to which that object can react. In code, usually attached to an event procedure
Object Oriented Object Oriented ProgrammingProgrammingClass – Provides a way to create
new objects based on a “meta-definition” of an object (Example: The automobile class)
Constructors – Special methods used to create new instances of a class (Example: A Honda Civic is an instance of the automobile class.)
OOP - EncapsulationOOP - EncapsulationIncorporation into a class of data & operations in one package
Data can only be accessed through that package
“Information Hiding”
OOP - InheritanceOOP - InheritanceAllows programmers to create
new classes based on an existing class
Methods and attributes from the parent class are inherited by the newly-created class
New methods and attributes can be created in the new class, but don’t affect the parent class’s definition
OOP - PolymorphismOOP - PolymorphismCreating methods which describe the way to do some general function (Example: The “drive” method in the automobile class)
Polymorphic methods can adapt to specific types of objects.
The Programming The Programming Development CycleDevelopment Cycle
Done after identifying inputs, processing & outputs
Steps1. Analyze the problem2. Plan a solution to the problem
(algorithm)3. Design the user interface
The VB.NET Programming The VB.NET Programming Development CycleDevelopment Cycle
Steps (continued)4. Code the solution5. Test and debug the solution6. Complete program documentation7. Begin to plan for next release
(start Cycle again)
1. Analyze the Problem1. Analyze the ProblemQuestions to ask:
◦Who is my intended audience?◦What SPECIFIC outcomes does my
audience expect?◦What business rules is my audience
expecting to have incorporated into the solution?
◦What is the SCOPE of the problem?
2. Plan a Solution 2. Plan a Solution (Algorithm)(Algorithm)What types of programming structures
are needed?◦ Sequential structures◦ Conditional structures◦ Looping structures
What data structures are needed?◦ Variables◦ Lists◦ Arrays
3. Design the User 3. Design the User InterfaceInterfaceAKA – The “UI”Is the UI “learnable”?Is it simple? (Limit user choices)Does the UI promote error-proof
use?Is the layout of the UI arranged in
a fashion conducive to the user’s culture and expectations?
4. Code the Solution4. Code the SolutionDevelop an actual program from
an algorithmShould be the “easiest” part of
the process – all the work should already be done!
5. Test & Debug the 5. Test & Debug the SolutionSolutionAlpha Testing – Internal testing done
with expected client data (NOT LIVE DATA)
Beta Testing – Testing done at the client site with their data (USUALLY LIVE DATA)
Try to predict common user errorsTest subjects should be Power Users,
Normal Users and Neophytes
6. Complete 6. Complete DocumentationDocumentationUser Documentation:
◦ User Manual◦ Technical Documentation (for System
Administrators)
Internal Documentation:◦ Documentation comments◦ Code comments◦ Procedural comments◦ Should be done while coding!
7. Plan Next Release7. Plan Next ReleaseWhat bugs need to be fixed?
◦Are bugs “critical”? (Need to be fixed in a minor release)
◦If bugs are not critical, they can be fixed in next major release
What product enhancements do the users want for the next release?
Internal CommentingInternal CommentingComments are non-executable lines (the
computer ignores them) which are used to communicate valuable information about code to others
Types of Internal Commenting:◦ Documentation Comments◦ Code Comments◦ Procedural Comments
Comment Syntax:◦ C-like Syntax (C, C++, Java, JavaScript):
/* This is a comment */ ◦ Visual Basic Syntax:
‘This is a comment
Documentation Documentation CommentsCommentsUsed to given specific
information about a programUsually found at the beginning of
a code windowInclude information about the
author, creation date, purpose, modification date & modification history
Documentation CommentDocumentation Comment'TITLE: Hello World, v2.0'AUTHOR: Bob Molnar'PURPOSE: To demonstrate changing of textbox 'properties using event procedures.'CREATED ON: 09.10.2002'LAST MODIFIED ON: 09.18.2002'LAST MODIFIED BY: RSM'MODIFICATION HISTORY:' 09.12.2002 - Renamed form to frmMain to' conform with accepted naming standards (MJK) ' 09.18.2002 - Created a Clear Button enabling' users to clear output (RSM)
NOTE: Example uses Visual Basic SyntaxNOTE: Example uses Visual Basic Syntax
Code CommentsCode Comments“Tell the story” of the code, in
EnglishFor this class, you should use
code comments to indicate what lines of code do
Code CommentsCode Comments
/* Initialize loop counter to 1 */counter = 1;/* Set loop to repeat 10 times */while(counter <= 10){ /* Prompt for input */ printf("Enter grade: "); /* Get user's input, store in the variable grade */ scanf("%d", &grade);} /* end while */
NOTE: Example uses C SyntaxNOTE: Example uses C Syntax
Procedural CommentsProcedural CommentsIdentify purpose, arguments &
return values for proceduresCan be used in:
◦Event Procedures◦Sub-Procedures◦Function Procedures
Procedural CommentsProcedural Comments' PROCEDURE: btnClear_Click' TYPE: Event Procedure' ARGUMENTS: VB-Generated' PROCEDURE: btnClear_Click' RETURNS: Nothing' PURPOSE: Re-sets the value of the textbox ' txtDspMsg to null when the button btnClear ' clickedPrivate Sub btnClear_Click(...) Handles _ btnClear.Click txtDspMsg.Text = ""End Sub
NOTE: Example uses Visual Basic SyntaxNOTE: Example uses Visual Basic Syntax
Questions?Questions?
ResourcesResourcesBob Molnar, N201 Lecture NotesVisual Basic.NET Primer Plus by
Jack Purdum (Sams Publishing, 2003)
An Introduction to Programming Using Visual Basic.NET Fifth Edition by David I. Schneider (Prentice Hall, 2003)
C: How to Program by Deitel & Deitel (Prentice Hall, 2004)