SoftwareSoftware

Reading Assignment: Ch 5Reading Assignment: Ch 5

Sohaib A KhanSohaib A Khan

CS101 - Wk06 - Regular CS101 - Wk06 - Regular LectureLecture

What is Software?What is Software?

Software is the Software is the instructions instructions that that run on a computerrun on a computer– Also called a computer Also called a computer programprogram

Two basic types: Two basic types: operating operating systems systems and and applicationsapplications

Written in a programming languageWritten in a programming language– E.g. V-BASIC (E.g. V-BASIC (BBeginners eginners AAll-Purpose ll-Purpose

SSymbolic ymbolic IInstruction nstruction CCode), C, C++, ode), C, C++, Java, FortranJava, Fortran

Types of Software Types of Software DistributionsDistributions

Commercial SoftwareCommercial Software– Created by a software house (Microsoft, Borland, Created by a software house (Microsoft, Borland,

Adobe), typically by large teams of programmersAdobe), typically by large teams of programmers– Some commercial software is Some commercial software is bundledbundled with hardware with hardware– Evaluation versions Evaluation versions may be free, low cost, or with may be free, low cost, or with

limited functionalitylimited functionality FreewareFreeware

– Software that can be copied and distributed at no costSoftware that can be copied and distributed at no cost– Author still retains the copyrightAuthor still retains the copyright

SharewareShareware– Software that can be used in trial period for free, then Software that can be used in trial period for free, then

the author expects a small paymentthe author expects a small payment– Mostly works on honor systemMostly works on honor system

Software VersionsSoftware Versions Commercial Software mostly goes through Commercial Software mostly goes through

extensive testing cyclesextensive testing cycles Alpha Release: Preliminary version, not yet ready Alpha Release: Preliminary version, not yet ready

for usefor use Beta Release: Test version, normally released to Beta Release: Test version, normally released to

consumers, helpful in identifying bugs…consumers, helpful in identifying bugs…– Often comes with disclaimersOften comes with disclaimers

Version 1 would typically follow the Beta releaseVersion 1 would typically follow the Beta release Subsequent versions indicate significant upgrades Subsequent versions indicate significant upgrades

in functionality, as well as lesser bugsin functionality, as well as lesser bugs– Version numbers or revision numbers tell you which Version numbers or revision numbers tell you which

release release you haveyou have– Replacing with a new release is called an Replacing with a new release is called an upgradeupgrade

Software BugsSoftware Bugs The original software bugThe original software bug

– Found by Dr Grace Hooper, Found by Dr Grace Hooper, 1945, in Harvard Mark II1945, in Harvard Mark II

Software Software BugBug: “A persistent : “A persistent error in software”… software error in software”… software not behaving as it shouldnot behaving as it should

DebuggingDebugging: Finding and : Finding and fixing problemsfixing problems

PatchPatch: A small upgrade sent : A small upgrade sent by manufacturer to remove by manufacturer to remove a certain bug from the a certain bug from the softwaresoftware

Some programmers may not Some programmers may not agree that their software agree that their software has a ‘bug’… ‘it’s-a-feature-has a ‘bug’… ‘it’s-a-feature-not-a-bug!’ syndromenot-a-bug!’ syndrome

Evaluating Commercial Evaluating Commercial SoftwareSoftware

Product reviews, e.g. in PC World or Product reviews, e.g. in PC World or PC Magazine, are very usefulPC Magazine, are very useful

Trial versions are often availableTrial versions are often available User discussion groups on the web User discussion groups on the web

often existoften exist Try Google!Try Google!

Useful Software CategoriesUseful 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 ReaderGoogle 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)

Software Suites and Works Software Suites and Works ProgramsPrograms

Software SuitesSoftware Suites– E.g. MS Office, LotusE.g. MS Office, Lotus– Several software applications in one Several software applications in one

packagepackage Works ProgramsWorks Programs

– E.g. MS WorksE.g. MS Works– Not for Not for power userspower users– Simplified inexpensive versionsSimplified inexpensive versions– Compatible with full versionsCompatible with full versions

Free SoftwareFree Software

Many download sites on the webMany download sites on the web– www.tucows.comwww.tucows.com– www.download.comwww.download.com

Need to be careful about security when Need to be careful about security when downloading executablesdownloading executables– Should have updated virus-scan software Should have updated virus-scan software

availableavailable Open Source software, under GNU licenseOpen Source software, under GNU license

– ““GGnu’s nu’s NNot ot UUnix”, “nix”, “GGreat reat NNew ew UUnix”, nix”, sponsored by Free Software Foundationsponsored by Free Software Foundation

Software PiracySoftware Piracy

Example: How Software Example: How Software WorksWorks