1. Software Reading Assignment: Ch 5 Sohaib A Khan CS101 - Wk06 - Regular Lecture

2. What is Software? Software is the instructions that run on a computer Software is the instructions that run on a computer –Also called a computer program Two basic types: operating systems and applications Two basic types: operating systems and applications Written in a programming language Written in a programming language –E.g. V-BASIC (Beginners All-Purpose Symbolic Instruction Code), C, C++, Java, Fortran

3. Types of Software Distributions Commercial Software Commercial Software –Created by a software house (Microsoft, Borland, Adobe), typically by large teams of programmers –Some commercial software is bundled with hardware –Evaluation versions may be free, low cost, or with limited functionality Freeware Freeware –Software that can be copied and distributed at no cost –Author still retains the copyright Shareware Shareware –Software that can be used in trial period for free, then the author expects a small payment –Mostly works on honor system

4. Software Versions Commercial Software mostly goes through extensive testing cycles Commercial Software mostly goes through extensive testing cycles Alpha Release: Preliminary version, not yet ready for use Alpha Release: Preliminary version, not yet ready for use Beta Release: Test version, normally released to consumers, helpful in identifying bugs… Beta Release: Test version, normally released to consumers, helpful in identifying bugs… –Often comes with disclaimers Version 1 would typically follow the Beta release Version 1 would typically follow the Beta release Subsequent versions indicate significant upgrades in functionality, as well as lesser bugs Subsequent versions indicate significant upgrades in functionality, as well as lesser bugs –Version numbers or revision numbers tell you which release you have –Replacing with a new release is called an upgrade

5. Software Bugs The original software bug The original software bug –Found by Dr Grace Hooper, 1945, in Harvard Mark II Software Bug: “A persistent error in software”… software not behaving as it should Software Bug: “A persistent error in software”… software not behaving as it should Debugging: Finding and fixing problems Debugging: Finding and fixing problems Patch: A small upgrade sent by manufacturer to remove a certain bug from the software Patch: A small upgrade sent by manufacturer to remove a certain bug from the software Some programmers may not agree that their software has a ‘bug’… ‘it’s-a-feature-not-a- bug!’ syndrome Some programmers may not agree that their software has a ‘bug’… ‘it’s-a-feature-not-a- bug!’ syndrome

6. Evaluating Commercial Software Product reviews, e.g. in PC World or PC Magazine, are very useful Product reviews, e.g. in PC World or PC Magazine, are very useful Trial versions are often available Trial versions are often available User discussion groups on the web often exist User discussion groups on the web often exist Try Google! Try Google!

7. Useful Software Categories Word Processing (Word) Spread Sheets (Excel) Databases (Access) Web Browsers (IExplorer, Firefox) Email (Outlook, Eudora, GMail) Image Editors (Paint, Photoshop IrfanView) Utilities (Winzip, Acrobat Reader Google Desktop) Video Editing (Virtual Dub, Primiere) Mathematical Computing (MATLAB, Maple, Mathematica) Programming (VB, VC++, Java) Animation (Flash, Shockwave) Games (Doom, Need for Speed) Internet (Yahoo Messenger, Skype, GoogleTalk) Security (McAfee, Symantec, Norton Antivirus) Presentation (Powerpoint)

8. Software Suites and Works Programs Software Suites Software Suites –E.g. MS Office, Lotus –Several software applications in one package Works Programs Works Programs –E.g. MS Works –Not for power users –Simplified inexpensive versions –Compatible with full versions

9. Free Software Many download sites on the web Many download sites on the web –www.tucows.com www.tucows.com –www.download.com www.download.com Need to be careful about security when downloading executables Need to be careful about security when downloading executables –Should have updated virus-scan software available Open Source software, under GNU license Open Source software, under GNU license –“Gnu’s Not Unix”, “Great New Unix”, sponsored by Free Software Foundation Software Piracy Software Piracy

10. Example: How Software Works