3/5/2009computer software1 introduction computer system hardware software hw kernel/os api...

3/5/2009 Computer software 1

IntroductionIntroduction

Computer System

•Hardware

•Software

HW

Kernel/OS

API

Application Programs

SW

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Software/ProgramSoftware/Program

Software or program is • a set of computer instructions that achieve specific tasks. • written in a specific language

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Programming LanguageProgramming LanguageEvolutionEvolution

First Generation Language – machine languageSecond Generation Language – assembly languageThird Generation Language – high level language

CC++BASICCOBOL……..

Programmer friendly

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General-Purpose General-Purpose Programming LanguagesProgramming Languages

C : operating system

C++ : applications

BASIC : easy to learn

COBOL : business applications

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System ProgramsSystem ProgramsExamplesExamples

Operating Systems

Utility programs

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Application ProgramsApplication ProgramsExamplesExamples

MS Word

Netscape Web Browser

MS PowerPoint

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SW/Program/CodeSW/Program/Code

Source code – text/ASCII

Object code - binary

Machine code - binary

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Compiler & LinkerCompiler & Linker

Compiler Linker

Source

Code

Object

Code

Executable

Code

Readable

by

human

Executable

by

machine

Machine codeText

Other

Object

Codes

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ExecutionExecution

User

Kernel/OS Executable

Coed

1

2

3

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Script LanguagesScript Languages

Shell Languages

JavaScript

VB script

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InterpreterInterpreter

Translation

Execution

Line by line

No binary code/machine code