1. Introducing Computer Science & Algorithms

2. Goals By 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

3. Types 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

4. Computer use is Pervasive Banking Air Traffic Space Travel Commerce Medicine Public Safety Education

5. Computer Components Hardware ◦ Physical components of a computer ◦ Examples: Mouse, keyboard, RAM, hard drives, processor, monitor Software ◦ Instructions that get the computer to do something ◦ Operating Systems & Applications ◦ Examples: Windows 2000, Microsoft Excel, WordPerfect, Netscape, Internet Explorer

6. What is Computer 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!

7. Algorithms 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?

8. Developing an Algorithm 1. 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?

9. Developing an Algorithm PROBLEM INPUT MODULE PROCESSES MODULE OUTPUT MODULE 4. Develop a HIPO chart

10. Developing 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?

11. Programs Sets of instructions that get the computer to do something Instructions are translated, eventually, to machine language using an interpreter or a compiler Programs may be a few lines or millions of lines of code

12. Programming Tasks All 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.)

13. Relationships in Programming Programmer – 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

14. Categories of Languages Machine Language ◦ Binary digits (bits – 1s and 0s) which are translated to electrical impulses that get the computer to do something ◦ “Native” language of computers Assembly Languages ◦ Group of basic commands which are more like English ◦ Tied to specific processors ◦ Still need to be translated to machine language

15. Categories of Languages High 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

16. More on High-Level Languages Operations 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.

17. More on High-Level Languages Procedural 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

18. Object Oriented Programming Object – 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

19. Object Oriented Programming Attribute – 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

20. Object Oriented Programming Class – 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.)

21. OOP - Encapsulation Incorporation into a class of data & operations in one package Data can only be accessed through that package “Information Hiding”

22. OOP - Inheritance Allows 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

23. OOP - Polymorphism Creating 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.

24. The Programming Development Cycle Done after identifying inputs, processing & outputs Steps 1.Analyze the problem 2.Plan a solution to the problem (algorithm) 3.Design the user interface

25. The VB.NET Programming Development Cycle Steps (continued) 4.Code the solution 5.Test and debug the solution 6.Complete program documentation 7.Begin to plan for next release (start Cycle again)

26. 1. Analyze the Problem Questions 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?

27. 2. Plan a Solution (Algorithm) What types of programming structures are needed? ◦ Sequential structures ◦ Conditional structures ◦ Looping structures What data structures are needed? ◦ Variables ◦ Lists ◦ Arrays

28. 3. Design the User Interface AKA – 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?

29. 4. Code the Solution Develop an actual program from an algorithm Should be the “easiest” part of the process – all the work should already be done!

30. 5. Test & Debug the Solution Alpha 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 errors Test subjects should be Power Users, Normal Users and Neophytes

31. 6. Complete Documentation User Documentation: ◦ User Manual ◦ Technical Documentation (for System Administrators) Internal Documentation: ◦ Documentation comments ◦ Code comments ◦ Procedural comments ◦ Should be done while coding!

32. 7. Plan Next Release What 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?

33. Internal Commenting Comments 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

34. Documentation Comments Used to given specific information about a program Usually found at the beginning of a code window Include information about the author, creation date, purpose, modification date & modification history

35. Documentation 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 Syntax

36. Code Comments “Tell the story” of the code, in English For this class, you should use code comments to indicate what lines of code do

37. Code 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 Syntax

38. Procedural Comments Identify purpose, arguments & return values for procedures Can be used in: ◦ Event Procedures ◦ Sub-Procedures ◦ Function Procedures

39. Procedural 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 ' clicked Private Sub btnClear_Click(...) Handles _ btnClear.Click txtDspMsg.Text = "" End Sub NOTE: Example uses Visual Basic Syntax

40. Questions?

41. Resources Bob Molnar, N201 Lecture Notes Visual 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)