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Computer software

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Definition : The set of instructions used to control hardwareand accomplish specific tasks are called software.

Functions :

Manage the computer resources of the organization.

Develop tools that human beings can utilize to take the

advantage of these resources.

Act as an intermediary between stored information and

organization.

Note : Earlier user interface used to be treated as the third

layer of software category. Now is a part of application

software.

Computer software

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Different types of software's can be illustrated as

Computer software

User interface

Application software

System software

Hardware

Types of software

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System software :

Definition : A software that directly interacts with the hardwareand comprise programs that manage the hardware

components.

Functions

Supervises the execution of all application softwareConvert high-level and 4GL programming codes into

computer executable form.

Manages resources like storage and memory, peripheral

devices like printer and monitor etc. Ex : operatingsystem.

Functionalities may be single-tasking or multi-tasking.

Computer software

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Application software

D

efinition : Program that help the user, the systemsoftware and the hardware to work together to solve theend user problems.

Special software languages are used to developapplication software.

Ex : Word processing software Can be purchased in stores and is called packages.

Custom software : A software designed and writtenbased on situation.

Free ware : Available in public domain and can be used

and altered without fee and restriction. Shareware : Author of the software assumes voluntary

contribution from the user.

Public domain : no copyright.

Open source :

Computer software

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Software generations First generation : Used machine language.

Second generation : Assembly language. (usedmnemonic codes)

Third generation : High level languages likeFORTRAN and COBOL. Program need to be

compiled using compiler. Fourth generation : Packaged software.

Languages like C, object oriented languages likec++ and java, WWW and development of GUI.

Fifth generation : Integrated software, animation,multimedia. NLP (natural language processor),HTML, XML, Active X and Active server pages.

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Operating system Definition : Is a set of programs that controls and

supervises a computer systems hardware and providesservice to application software, programmers, andusers of a computer system.

Functions :

Allocation of resources to the application jobs in theexecution queue.(resource management)

Provides locations for data and programs in main memoryand controls input and output devices.(memorymanagement)

Free space management, disk scheduling and storageallocation. (Secondary-storage management)

Schedules the jobs submitted.(process management)

Provides a pleasant and effective user interface. (command interpreter system)

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Functions :

Creates and deletes files and directories

(File management)

Controlling access to programs, processes and users.

( Protection system)

Deals with h/w specific drivers for devices and keeps it all hidden

form the rest of the system. ( I/O system management)

Generalizes network access. ( Networking)

Operating system

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Types of operating systems Single user system :

Allows one program to be executed at a time.

Often found in personal computers. Ex:Microsoftswindows.

Multiprogramming system :Permits multiple programs to share systems

resources through concurrent usage of CPU.

Programs appear to be executed simultaneously.

Increases the overall performance of the CPU.CPU devotes time to processing instructions from

one program while another goes through I/Ooperations.

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Time-sharing system :

Allows multiple users to access a single computer system.CPU shifts among users on a timed basis, by allocating

specific periods of time and it appears as each user hasuninterrupted access to the CPU.

When an interrupt occurs, the OS may switch to anotherprogram before a full time slice is used.

Multiprocessing system :

Allows simultaneous execution of programs by a computer

that has two or more CPUs. Mainframe and supercomputers.

A single large main CPU may be connected to multiplechannels which handles input and output from the mainCPU and coordinates the work of slower I/O devices.

Types of operating systems

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Virtual-Storage System :Developed after some limitations was faced in

multiprogramming.

Secondary memory as an extension of primary storage.

Gives an illusion of having maximum amount of primarymemory.

Portions of a program can be swapped between primary andsecondary storage devices.

Paging is another extension of this concept, where pages arekept on secondary storage devices in and out of primarystorage as needed.

Virtual machine (VM) : Is a very powerful program that can run several operating

systems at one time.

Allows several users of a computer system to operate as ifeach had the only terminal attached to the computer.

The user can select the OS which compatible with theintended application.

Types of operating systems

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Types of information processing

Batch processing : Data is collected and storedbefore processing.

Real-time processing : Transactions areprocessed on a real time basis. Ex : All internet

based transactions. Railway or airline ticketbooking.

Distributed processing :

Parallel processing :

Sequence scheduling : next program is selectedbased on priority.

Concurrent scheduling : Concurrent processing oftwo or more programs.

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Types of Application s/w Content access software

End-User software ( document mgmt, scheduling,accounting mgmt)

Enterprise software (SCM, CRM, product life cycle

mgmt) Simulation software

Examples of application software Word processing software

Spread sheet software Presentation software

Database software

Communication software

Accounting and financial software

Project management

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Types of Application s/w

Project management Projects like developing of software, publishing a news letter,

implementing a training programme, starting a new business

or even building a new home are done by managers.

Project management software helps to put together a plan of

action, compile and organise all details to be completed.

Ex : MS-project