Computer Software and Systems (1)

7/31/2019 Computer Software and Systems (1)

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Computer Software and Systems


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Software

n Series of instructions written forthe computer to do functions.

n

Typically composed of many files.n Contains data that is necessary for

providing facts, records and other

information.e.g. Help documentation, spell

checker, thesaurus, library etc.


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How Does Software Work?

n Microprocessor understands onlymachine language.

n Runs on signals produced by 2

behaviors:

Flow (represented by the bit 1) and

No Flow (represented by the bit 0)Instructions were written in a High-Levellanguage must be translated to machine

language before a computer use them.


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2 Special Programs used forTranslationn COMPILERS - Translate ALL instructions in

a program as a single batch & theresulting machine language instructions,

called object code, are placed in a newfile.

n INTERPRETER Converts an instructionat a time while the program is running.n Reads 1st the instruction, converts it into

machine language and then sends tomicroprocessor.


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Classification of Software

n SYSTEM SOFTWAREn Series of instructions written for the

computer to do BASIC & GENERAL

functions such as booting, opening files,saving, printing.

nAPPLICATION SOFTWARE

nWritten for the computer to do specificfunctions such as creating documents,crunching numbers, doing presentations ormovies, drawing pictures, and editing

photographs.


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SOFTWARE

n System Softwaren Operating System (OS)

n DOS

n

Windowsn MacOS

n Linux

n UNIX

nDevice DriversnUtilities

n Programming Languages


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SOFTWARE

nAPPLICATION SOFTWAREn Documental Production

n Spreadsheet

n

Presentation, Animationn Graphics

n CAD, CAM

n

Accounting & Financen Mathematical & Statistical

n Entertainment, Music, Video

n Educational


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Operating System

n Main program in a system software.n Acts as a MASTER Controller for all routine activities

that takes place within a computer system.

n Manages RAM by allocating specific areas & sizes ofmemory for each program.

n OS must see to it that instructions & data from 1area of memory do not leak into an area allocated

to another program. Failing to do this it will causedata to be corrupted & program to crashed

n Ctrl+Alt+Del key by PRESSING this keys the PCmay recover from MEMORY LEAK or CRASHED


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DOS (Disk Operating System)

n

Provides basic interface between the userand the hardware and software.

2 TYPES of OS INTERFACE

1. DOS present a BLANK Screen to theuser, user submits commands

to type

2. GUI (Graphical User Interface) supports GRAPHIC images called

icons


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GUI History

n 1979- Steve Jobs of Apple Computers decideto abandon the DOS. They moved to a newproduct to be called MACINTOSH. Idea was a

result from a visit to a XEROX lab.n 1984 MACINTOSH 1st introduced GUI, and

called Computer for Everybody

n Bill Gates Founder & CEO of the MicrosoftCorp.. Quickly recognized the need to providea GUI product & immediately developed

Windows.


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OPEN SOURCE

andFREE SOFTWARE


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OPEN SOURCE SOFTWARE (OSS)

n Defined by the Open Source Initiative(OSI)

n (

http://www.opensource.org/docs/definitio)

n The license must allow modificationsand derived works, and must allowthem to be distributed under the same

terms as the license of the original
http://www.opensource.org/docs/definition_plain.phphttp://www.opensource.org/docs/definition_plain.php


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FREE SOFTWARE

n Is a matters of users freedom to run, copy,distribute, study, change, & improve thesoftware.n 4 KINDS of FREEDOM

1. Freedom to RUN the program (freedom 0)

2. Freedom to study how the program works &

adapt it to your needs (freedom 1). Accessthe to the source code is a precondition forthis.


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3. Freedom to redistribute copies so youcan help your neighbor (freedom 2)

4. Freedom to improve the program &

release your improvements to thepublic so that the whole communitybenefits (freedom 3). Access to the

source code is a precondition for this.


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LINUX

n Developed by Linus Torvalds of Finland.n Distributed free in the WEB and as

distribution in CDs.

n Has GPL (General Public License) allowprogrammers to use LINUX utilities.

n With features of multitasking, virtual

memory, multi-user capabilities.n Popular operating system for email, web

servers and local area networks.

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Computer Software and Systems (1)