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Computer Programs and Programming Languages

Computer Programs and Programming Languages. What is a computer program ?. Set of instructions that directs computer to perform tasks. Programming language —used to write instructions. Computer Programs and Programming Languages. What are low-level languages and high-level languages?.

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Computer Programs and Programming Languages

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  1. Computer Programs and Programming Languages • What is a computer program? • Set of instructions that directs computer to perform tasks • Programming language—used to write instructions

  2. Computer Programs and Programming Languages • What are low-level languages and high-level languages? Low-levellanguage High-level language Machine-dependentruns only on one type of computer Oftenmachine-independentcan run on many different types of computers Machine and assembly languages are low-level

  3. Low-Level Languages • What is machine language? • Only language computer directly recognizes

  4. Low-Level Languages • What is assembly language? • Instructions made up of symbolic instruction codes, meaningful abbreviations and codes • Source program contains code to be converted to machine language

  5. Procedural Languages • What is a procedural language? Programmer writes instructions that tell computer what to accomplish and how to do it Uses series of English-like words to write instructions Often called third-generation language (3GL) Most widely used are BASIC, COBOL, and C

  6. Procedural Languages • What is a compiler? • Program that converts entire source program into machine language before executing it

  7. Procedural Languages • What is an interpreter? • Program that translates and executes one program code statement at a time • Does not produce object program

  8. Procedural Languages • What is BASIC? • Designed for use as simple, interactive problem-solving language • Beginner’s All-purpose Symbolic Instruction Code

  9. Procedural Languages • What is COBOL? • Designed for business applications • English-like statements make code easy to read, write, and maintain • COmmon Business-Oriented Language

  10. Procedural Languages • What is C? • Powerful language originally designed to write system software • Requires professional programming skills

  11. Object-Oriented Programming Languages • What is an object-oriented programming (OOP) language? Used to implement object-oriented design Major benefit is ability to reuse existing objects Event-driven—checks for and responds to set of events C++ and Java are complete object-oriented languages Objectis item that contains data and procedures that act on data Eventis action to which program responds

  12. Object-Oriented Programming Languages • What is C++? • Includes all elements of C, plus additional features for working with object-oriented concepts • Used to develop database and Web applications

  13. Object-Oriented Programming Languages • What is Java? • Developed by Sun Microsystems • Similar to C++ but uses just-in-time (JIT) compiler to convert source code into machine code

  14. Object-Oriented Programming Languages Visual programming environment (VPE) allows developers to drag and drop objects to build programs Programmer writes and implements program in segments • What is a visual programming language? Provides visual or graphical interface for creating source code Sometimes calledfifth-generation language Often used in RAD (rapid application development) environment

  15. Object-Oriented Programming Languages Step 1. The programmer designs the user interface. Step 2.The programmer assigns properties to each object on the form. Step 3.The programmer writes code to define the action of each command button. Step 4.The programmer tests the application. • What is Visual Studio 2005? • Suite of visual programming languages and RAD tools • .NET is set of technologies that allows program to run on Internet • Visual Basic 2005 is used to build complex object-based programs

  16. Object-Oriented Programming Languages • What is Delphi? • Powerful visual programming tool • Ideal for large-scale enterprise and Web applications

  17. Object-Oriented Programming Languages • What is PowerBuilder? • Another powerful visual programming tool • Best suited for Web-based and large-scale object-oriented applications

  18. Nonprocedural Languages and Program Development Tools • What are nonprocedural languages and program development tools? Nonprocedural LanguageThe programmer writes English-like instructions or interacts with a visual environment to retrieve data from files or a database Program Development ToolsUser-friendly programs designed to assist both programmers and users in creating programs

  19. Nonprocedural Languages and Program Development Tools • What is RPG (Report Program Generator)? • Nonprocedural language used for generating reports, performing computations, and updating files

  20. Nonprocedural Languages and Program Development Tools • What is a fourth-generation language(4GL)? • Nonprocedural language that allows access to data in database • Popular 4GL is SQL, query language that allows users to manage data in relational DBMS

  21. Nonprocedural Languages and Program Development Tools • What is an application generator? • Program that creates source code or machine code from specification • Consists of report writer, form, and menu generator • Form provides areas for entering data

  22. Nonprocedural Languages and Program Development Tools • What is Visual Basic for Applications (VBA)? • Macro programming language • Macro—series of statements used to automate tasks

  23. Web Page Development • What is HTML (Hypertext Markup Language)? • Used to create Web pages

  24. Web Page Development ActiveX controlsmall program that runs on client Scriptinterpreted program that runs on client Appletusually runs on client, but is compiled Servletapplet that runs on server Processing formcollects data from visitors to Web site Countertracks number of visitors to Web site Image mapgraphic image that points to URL • How are special effects and interactive elements added to a Web page?

  25. Web Page Development Step 1. The programmer stores the CGI program in a special folder on the Web server such as /cgi-bin. Step 2. The Webmaster creates a link between the CGI program and Web page. When a user displays the Web page, the CGI program automatically starts. Step 4. The CGI program receives information from the database, assembles it in an HTML format, and sends it to the user’s Web browser. Database • What is the common gateway interface (CGI)? • Communications standard that defines how Web server communicates with outside sources • CGI script—program that manages sending and receiving across CGI Step 3. When the user submits a request, it is sent to the CGI program. The CGI program contacts the database and requests information for the user. In this case, it looks for a movie titled The Wizard of Oz.

  26. Web Page Development • What is a scripting language? • Typically easy to learn and use • JavaScript—adds dynamic content and interactive elements to Web page • VBScript (Visual Basic, Scripting Edition)—adds intelligence and interactivity to Web page • Perl (Practical Extraction and Report Language)—has powerful text processing capabilities

  27. Web Page Development • What is dynamic HTML (DHTML)? • Allows developers to include more graphical interest and interactivity in Web page

  28. Web Page Development • What are XHTML, XML, and WML? Includes features of HTML and XML XHTML(ExtensibleHTML)enables Web sites to be displayed more easily on microbrowsers XML(ExtensibleMarkupLanguage)allows developers to create customized tags Server sends entire record to client, enabling client to do much of processing without going back to server WML(WirelessMarkupLanguage)allows developers to design pages specifically for microbrowsers Useswireless application protocol (WAP), standard that specifies how wireless devices communicate with Web

  29. Web Page Development DreamweaverMX FlashMX FrontPage2003 • What is Web page authoring software? • Creates sophisticated Web pages without using HTML • Generates HTML

  30. Multimedia Program Development • What is multimedia authoring software? • Combines text, graphics, animation, audio, and video into interactive presentation • Used for computer-based training (CBT) and Web-based training (WBT) • Software includes Toolbook, Authorware, and Director

  31. Other Programming Languages • What are other available programming languages? ADA ALGOL APL FORTH FORTRAN HYPERTALK LISP LOGO MODULA-2 PASCAL PILOT PL/I PROLOG SMALLTALK

  32. The Program Development Cycle • What is the program development cycle? • Steps programmers use to build computer programs • Programming team—Group of programmers working on program

  33. Step 1 — Analyze Requirements • What is involved in analyzing the requirements? • Review requirements • Meet with systems analyst and users • Identify input, output, processing, and data components • IPO chart—Identifies program’s inputs, outputs, and processing steps

  34. Step 2 — Design Solution Object-oriented design Structured design, sometimes called top-down design Programmer begins with general design and moves toward detailed design • What is involved in designing the solution? Devise solution algorithm, step-by-step procedure to solve problem Two approaches

  35. Step 2 — Design Solution • What is a hierarchy chart? • Shows program modules graphically • Also called structure chart

  36. Step 2 — Design Solution • What is object-oriented (OO) design? • Programmer packages data and procedure into single unit, an object • Objects are grouped into classes • Class diagram represents hierarchical relationships of classes graphically

  37. Step 2 — Design Solution • What is a sequence control structure? • Control structure that shows actions following each other in order • Control structure depicts logical order of program instructions

  38. Step 2 — Design Solution • What is a selection control structure? • Tells program which action to take, based on a certain condition • Two types • Case control structure • If-then-else control structure—yields one of two possibilities: true or false

  39. Step 2 — Design Solution • What is a case control structure? • Yields one of three or more possibilities

  40. Step 2 — Design Solution Do-While Control Structure Do-Until Control Structure • What is a repetition control structure? • Enables program to perform one or more actions repeatedly • Do-while control structure—repeats as long as condition is true • Do-until control structure—repeats until condition is true

  41. Step 2 — Design Solution • What is aprogram flowchart? • Graphically shows logic in solution algorithm

  42. Step 2 — Design Solution • What is an example of a flowchart?

  43. Step 2 — Design Solution • What is flowcharting software? • Used by programmers to develop flowcharts

  44. Step 2 — Design Solution • What is pseudocode? • Uses condensed form of English to convey program logic

  45. Step 3 — Validate Design Check program design for accuracy Programmer checks logic for correctness and attempts to uncover logic errors • What is involved in validating the design? Desk checkprogrammers use test data to step through logic Logic errordesign flaw that causes inaccurate results Structured walkthroughprogrammer explains logic of algorithm while programming team steps through program logic Test datasample data that mimics real data that program will process

  46. Step 4 — Implement Design • What is implementation? • Writing the code that translates the design into a program • Syntax—rules that specify how to write instructions • Comments—program documentation • Extreme programming (XP)—coding and testing as soon as requirements are defined

  47. Step 5 — Test Solution • What is involved in testing the solution? Ensure program runs correctly and is error free Debugging—locating and correcting syntax and logic errors, orbugs Test copy of program, called beta, sometimes used to find bugs

  48. Step 6 — Document Solution • What is involved in documenting the solution? • Programmer performs two activities Reviews program code—removes dead code, program instructions that program never executes Reviews documentation

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