Computer Software and Operating System

8/19/2019 Computer Software and Operating System

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CHAPTER 2

Computer Software

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A computer system consists of two parts:

• Computer hardware, which constitutes the physical

components

• Computer software, which tells the hardware what to do

and how to do it

INTRODUCTION TO COMPUTER

SOFTWARE

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COMPUTER SOFTWARE

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Also known as programs. (Soul of Computer)

Collections of instruction for a computer.

Solve user problem and control different

operation.Computers requires program to function,

typically executing the program’s instruction in

CPU.

Software may be categorized along functionallines:-System software

Application software.


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Computer games software

Driver software

Educational software

Media players and media development software

Productivity software

Operating systems

EXAMPLES OF COMPUTER

SOFTWARE

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CLASSIFICATION OF SOFTWARE

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Software

Application

SoftwareSystem software

Operating system Utility software

Device

Driver

Language

Translator


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OPERATING SYSTEM (OS)

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Interface between hardware and user.Responsible for the management andcoordination of activities.

Sharing of the resources of the computer thatacts as a host for computing application run onthe machine.

Application program makes the use of OS bymaking request for services.

Linux, Windows.


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UTILITY SOFTWARE

It is also known as service program, service routine,

tools or utility routine.

It is computer software designed to help manage and

tune computer hardware, operating system or

application software by performing a single task or

small range of tasks.

Some utilities are integrated in major OS.

Examples: Disk storage Utilities (Disk Defragmenters,

Disk Checkers, Disk Cleaner, Disk Space Analyzer,

Disk Partition, file managers).

System Profiler.

Anti-virus software. etc.8


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Disk Cleanup:

It can find files that are unnecessary to computer

operation or take up considerable amount of

space.

Disk cleanup helps the user to decide what to

delete when their hard disk is full.

Disk clean up targets:

Compression of old files.

Temporary internet files.

Downloaded program files.

Recycle BinSetup log files. etc.

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Disk defragmenter:

It is a computer program in MS - Window designed to

increase access speed by rearranging files stored indisk to occupy contiguous storage location, a technique

commonly known as decrementing.

The purpose is to optimize the time it takes to read

and write files to/from the disk by minimizing head

travel time and maximizing transfer rate.

Antivirus software

Disk compression

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Device DriversDevice Drivers is software that permits a computer

system to communicate with a device.We install device and its driver before using a device.

Eg. Modem driver, printer driver etc.

Language ProcessorsLanguage processors is software that converts a source

program into object program.

For example C-compiler converts a program written in

C language into object program (machine code).

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APPLICATION SOFTWARE

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It is a computer software designed to perform a

specific function directly for the user or in some case

for another application program.

They are designed to run on an operating system for

the fulfilling various purposes and functionalities.

Also called software applications, applications or

apps.

Productive software, Presentation software, graphics

software, CAD, specialized scientific application,

industry specific software.Can be Categorized intoTailored Software

Packaged Software


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CONTD…

Tailored software is that software that are

specially designed and developed specific job or

task.

For e.g. school billing system, result processing

system, printing of certificates, etc.

Packaged Software is that software that is

generalized set of programs designed and

developed for the general purpose.

For e.g. Microsoft Office, Adobe Package, Tally,

Fact, etc.13


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Classification of Computer Software

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OPERATING SYSTEM

An operating system is a program that acts as an

interface between the software and the computer

hardware.

It is an integrated set of specialized programs

that are used to manage overall resources and

operations of the computer.

It is specialized software that controls and

monitors the execution of all other programs that

reside in the computer, including applicationprograms and other system software.


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Relationship Between Hardware , System Software,

and Application Software

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OPERATING SYSTEM


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Third Generation (mid 1960 to mid 1970):

Multimode operating system is implemented in IBM

system/360 in 1964

The batch processing systems were developed to processmany jobs at a time to utilize maximum computer

resources to accomplish multiprogramming concepts

Fourth Generation (mid 1970 to present):

The design of large scale integration (LSI) had majorrole in development of advance level operating system

This generation is very efficient due to many fantastic

changes to control memory, files, input/output devices

and many peripherals.

The personal computer becomes available for all due tomicroprocessor and OS is dramatically spread over

market.

The MS-DOS and UNIX operating systems were most

dominant OS in the beginning of 4th

generation.

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TYPES OF OPERATING SYSTEM

On basis of mode of useSingle user OSMulti-user OS

On basis of processing modeBatch processing

MultiprogrammingMultitaskingReal time systemDistributed OS

On basis of user interface

Command/ character based user interface (CUI)Graphical user interface (GUI)


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ON THE BASIS OF MODE OF USE

Single user OS:It is usable by single user, at a time

It supports only one program at a time

These are used on general PC and other hand held devices

The MS-DOS, PC-DOS etc. are single user interface An example of a this kind of operating system would be

found on a mobile phone. There can only be one user using

the mobile and that person is only using one of its

applications at a time.

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MULTI-USER OS:

OS that allows multiple user to access a computer

system concurrently is multi-user OSWhen more than one user is processing data at a same

time using one CPU is called multi-user or Time

sharing system

In this OS each operator has a time slice to accomplishhis/her process using processor

Time slice is small time allotted by OS to each operator

for utilization of processor

Its value is so small, so each operator feels thatprocessor is processing his/her job only

They are mostly found in supercomputer and

mainframe computer

Examples: UNIX, LINUX

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ON THE BASIS OF

PROCESSING MODE

Batch Processing:

In Batch processing same type of jobs batch(BATCH- a

set of jobs with similar needs) together and execute at a

time.The OS was simple, its major task was to transfer

control from one job to the next.

The job was submitted to the computer operator in form

of punch cards. At some later time the output appeared.

Common Input devices were card readers.

Batch processing has been associated with mainframe

computers since the earliest days of electronic

computing in the 1950s23


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MULTIPROGRAMMING

Multiprogramming is a technique to execute number ofprograms simultaneously by a single processor.

In Multiprogramming, number of processes reside in

main memory at a time.

The OS picks and begins to executes one of the jobs in themain memory.

If any Input/Output wait happened in a process, then

CPU switches from that job to another job.

Hence CPU in not idle at any time.


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The main memory consists of 5 jobs at a time, the CPU

executes one by one.

Advantages:

Efficient memory utilization

Throughput increases

CPU is never idle, so performance increases.


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MULTITASKING

Multitasking refers to term where multiple jobs areexecuted by the CPU simultaneously by switching

between them.

Operating System handles multitasking in the way that

it can handle multiple operations / executes multipleprograms at a time.

Multitasking Operating Systems are also known as Time-

sharing systems.

These Operating Systems were developed to provideinteractive use of a computer system at a reasonable cost.

A time-shared operating system uses concept of CPU

scheduling and multiprogramming to provide each user

with a small portion of a time-shared CPU.


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MULTIPROCESSING

Multiprocessoroperating system refers to the

use of two or more central operating unit (CPU)

within a single computer system.

These multiple CPUs are in a close

communication sharing the computer bus,

memory and other peripheral devices.

These types of systems are used when very high

speed is required to process a large volume of

data.


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REAL TIME OPERATING SYSTEM

There is also a Operating System which is known as

Real Time Processing System. In this OS Response

Time is already fixed.

It Means time to Display the Results after Possessing

has fixed by the Processor or CPU.Real Time System is used at those Places in which we

Requires higher and Timely Response

Eg: Hotel reservation, Attendance system.

There are two Types of Real Time System A Hard Real-Time System

A Soft Real Time System


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Distributed systems provide the following

advantages:

1 Sharing of resources.

2 Reliability.

3 Communication.

4 Computation speedup.


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FUNCTION OF OPERATING SYSTEM

Memory Management --keeps tracks of primary memoryi.e. what part of it is in use by whom, what part is not in use

etc. and allocates the memory when a process or program

requests it.

Processor Management --allocates the processor(CPU) to a

process and de-allocates processor when it is no longer

required.

Device Management --keeps track of all devices. This is

also called I/O controller that decides which process gets the

device, when, and for how much time.File Management --allocates and de-allocates the resources

and decides who gets the resources.

Security --prevents unauthorized access to programs and

data by means of passwords and similar other techniques.


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Control over system performance --records delays

between request for a service and from the system.

Interaction with the operators --The interactionmay take place via the console of the computer in the

form of instructions. Operating System acknowledges

the same, does the corresponding action and informs the

operation by a display screen.

Error-detecting aids --Production of dumps, traces,

error messages and other debugging and error-detecting

methods.

Coordination between other software and users

Coordination and assignment of compilers, interpreters,

assemblers and other software to the various users of

the computer systems.


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COMPILER• Acompiler is a special type of program that transforms the source

code written in a programming language (the source language) into

the machine language, which uses only two digits—0 and 1 (the target

language).

• The resultant code in 0s and 1s is known as the object code. The

object code is used to create an executable program.

• When executing , the compiler first parses (or analyzes) all of the

language statements syntactically one after the other and then, builds

the output code, making sure that statements that refer to other

statements are referred to correctly in the final code36


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INTERPRETER

Like the compiler, theinterpreteralso executes

instructions written in a high-level language.

The interpreter translates the instructions into an

intermediate form, which it then executes.

An interpreter is a computer program that

directly executes, i.e. performs, instructions written in

a programming or scripting language, without

previously compiling them into a machine

language program.37


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ASSEMBLER

An assembler is a program that takes basic computer

instructions and converts them into a pattern of bits

that the computer's processor can use to perform its

basic operations.

Some people call these instructions assemblerlanguage and others use the term assembly language.

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LINKER AND LOADER Also calledlink editoror binder

A program that combines the object modules to form anexecutable program In case of a large program, programmers prefer to

break the code into smaller modules, as this simplifies

the programming task When the source code of all the modules have beenconverted into object code, all the modules need to be

put together, which is done by the linker Compiler automatically invokes the linker as the last

step in compiling a program Loader is a special type of program that copies

programs from a storage device to the main memory,

where they can be executed Most loaders are transparent to the users

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Assemblers Assembly languages are more easily translated in to

machine code than high-level programs languages.

Each assembly language statement directly corresponds to

one or more machine instructions.

Another way to think about this is that assembly language

code is simply an abbreviated form of machine code.

Thus, to transform a program from an assembly language tomachine code all that must be done is that the instructions

must be converted from their mnemonic abbreviations into

their equivalent string of ones and zeroes.

This transformation process is known as assembling and is

accomplished by an assembler.

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Compilers A compiler is a computer program that converts an entire

program written in a high-level language (called source

code) and translates it into an executable form (called object

code).

Interpreters An interpreter is a computer program that takes source

code and converts each line in succession. At each step it executes the high-level statement.

In other words, it doesn't have to examine the entire

program before it can begin executing code.

Thus, programs that are interpreted lend themselves to

interactive programming.

However, programs that are interpreted will generally run

much slower than programs that are compiled.43

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Computer Software and Operating System