1. Programming Concepts and Languages Chapter 12 – Computers: Understanding Technology, 3 rd edition 1November 17. 2008

2. Terminology A program is a set of instructions telling a computer how to perform a task The program is written in a programming language The programming language instructions are referred to as source code and the act of writing source code as coding 2November 17. 2008

3. Programming Languages Fewer words and symbols and simpler syntax than natural language Can either be low-level or high-level Elements are variables, executable statements, decision statements, looping Algorithm (complete list of steps for solving a problem) often written in pseudocode (high level language meant to describe steps) and then programmer writes in programming language 3November 17. 2008

4. Reusable Code Certain problems or tasks recur in programming so it is desirable to avoid “reinventing the wheel” when this occurs Subroutine or function to do certain tasks – the idea is that one needs to understand what inputs it needs and what outputs it produces but not how it works 4November 17. 2008

5. Program Execution Some computer languages require a compiler, a computer program which translates the programming language source code into machine code Other languages are executed via interpreters 5November 17. 2008

6. Documentation Tools Flowcharts – Visual representation of algorithm – different shaped boxes are used for different types of statements (e.g. process, decision, data input/output) Comments – Messages in programs that explain source code to later readers 6November 17. 2008

7. Programming Errors Syntax errors Logic errors Runtime errors 7November 17. 2008

8. Programming Languages Assembly languages – uses symbols and words to represent elements of machine language – 1 assembly language statement generally produces 1 machine code statement COBOL (1960) – business applications language RPG – Report Program Generator (IBM AS/400 mainframe) 8November 17. 2008

9. Programming Languages (cont.) FORTRAN (1957) – dominated math and scientific programming BASIC – interpreted language, originally developed as teaching tool Visual Basic (VB) – language of choice for developing software prototypes Visual Basic.Net (ITP 112, ITP 212) C (ITP 130, ITP 230) – elements of both BASIC and assembly language, runs fast 9November 17. 2008

10. Programming Languages (cont.) C++ (ITP 132, ITP 232) - superset of C C# (ITP 136) - derived from C++ and Java Java – (ITP 120, ITP 220, ITP 246) - cross-platform flexibility; when used in web pages, called applets, but this is rarely done now; web use is primarily server-side 10November 17. 2008

11. Scripting Languages JavaScript (ITD 210, ITP 140, ITP 225) VBScript Perl 11November 17. 2008

12. Markup Languages HTML – Hypertext Markup Language (ITD 110) XHTML – Extensible Hypertext Markup Language XML – Extensible Markup Languages WML – Wireless Markup Language 12November 17. 2008