Types of Computer Software

Computer Software

Is a Term used for organized collections of computer data and instructions.

Computer programs are also usually referred to as computer

Software. A Computer Program is a set of instructions given to the computer to solve

Particular problem. Computer program specify a sequence of operations that

Computer will perform.

Computer Software is further divided into two major categories

  • System Software
  • Application software


System Software refers to the programs that are responsible for controlling and

Managing the actual operations of the computer hardware. Generally system software

Consists of an operating system and some fundamental utilities such as disk formatters,

Managers, display managers, user authentication (login) and network control




Application Software is used to accomplish tasks specified by the user. Application

May consist of a single program, such as an image viewer or a collection of

Programs (called software package) that work together to accomplish a task. e.g.

Word processors, spreadsheet, database etc.

 Organization of Computer

A computer performs the following five major functions:

  • Accepts data or instructions from input device
  • Stores data
  • Processes data as required by the user
  • Gives results in the form of output
  • Controls all operations inside a computer.

In order to perform above mentioned operations; the computer system is divided

Into three units. These are

  • Central processing unit (CPU),
  • Memory unit
  • Input / Output units

 Central Processing Unit (CPU)

He Central Processing Unit (CPU) is generally referred to as the brain of the

Computer. The primary work of CPU is to convert data from Input, process the data and output in useful information that can be used by either user or other

Programs. Central processing unit (CPU) is a highly complex set of electronic

Circuitry that

Executes program

Instructions. It is like a really fast

Calculator that has the ability to recall

Numbers from various locations in

Memory, perform arithmetic and logical

Operations with them, such as addition

Or multiplication, and then store the


All computers must have a

Central processing unit. As Figure 2.3

Shows, the central processing unit

Consists of two main parts: The control

Unit, arithmetic and logic unit. Each part

Has a specific function.




Arithmetic and Logic Unit (ALU)

The Arithmetic and Logic Unit (ALU) consists of electronic circuitry that

Executes all arithmetic and logical operations.

The arithmetic and logic unit can perform the following operations, like:

  • Addition
  • Subtraction
  • Multiplication
  • Division
  • Logical Operations

A logical operation is usually a comparison of numbers, letters, or special

Characters. The computer can then take action based on the result of the comparison.

This is a very important capability. It is by comparing that a computer is able to tell,

For example, whether there are available seats on train, whether mobile phone

Customers have exceeded their pre-paid credit limits etc.

Logical operations can test for three conditions:

  • Equal-to condition: The arithmetic and logic unit compares two values to

Determine if they are equal. For example, if the number of tickets s d

Equals the number of seats in the hall, then no more tickets are available

Less-than condition: The computer compares values to determine if one

Less than another. For example, if the hours a person worked this week

Are less than 35, then some fine is deducted from his salary.



Greater-than condition.

The computer determines if one value is greater

Than another. For example, if the hours a person worked this week are

Greater than 40, then he gets bonus for working overtime.

Control Unit (CU)

The Control Unit consists of circuitry that generates signals to direct the entire

Computer system to carry out or execute the programs. The control unit itself does not

Execute program instructions; rather, it directs other parts of the system to do so. The

Control unit must communicate with the arithmetic and logic unit, memory and other

Of computer system.

It also controls the flow of information through the processor, and coordinates

Activities of the other units. This unit also provides clock pulses. Clock pulses are

In addition to the ALU and CU (Control Unit), the processor has a number of

Locations to store information that is currently being processed. These are

Registers. These are temporary storage areas for instructions or data. Registers

Managed by the control unit to accept, hold, and transfer instructions or data and

Arithmetic or logical comparisons at high speed.

System bus

The CPU must be able to communicate with all devices. The devices are

Together by a communications channel called a bus. A ‘bus is composed of

“f communication lines or wires. It is used to move large amount of bits in the

Electrical pulses from a specified source to a specified destination. The bus is

  • Central Processing Unit

* Control Unit

* Arithmetic and Logic Unit

Main memory (RAM, ROM)

  • Input / Output Devices

Bus is the common path which is used to send /receive data and commands

To / from CPU and memory and all input / output devices. It is also used to send /

Receive data from secondary storage. The capacity of a bus depends upon the number

Of data lines it contains. Bus with 16 lines can carry 16-bits (2 Bytes) at a time where

Bus with 32 lines can carry 32-bits (4 Bytes) at a time and so on. There are three

Different buses in the computer system.

  • Data Bus
  • Address Bus
  • Control bus




 Data Bus

The most common bus is the data bus. A data bus carries data. It is

Electrical path that connects the central processing unit (CPU), memory, input / output

Devices and secondary storage devices. The bus contains parallel group of lines. The

Number of lines in the bus affects the speed at which the data travels between

Different components. Just like the number of lanes on a motorway affect the amount

Of number of lanes on road means more cars can pass through it.

More lines are present in the bus, it can carry more data. E.g. a bus with 16 lines c

Carry 16 bits (2 bytes) and a bus with 32 lines can carry 32 bits (4 bytes) of data.

Busses are designed in such a way that they can communicate with the

Components in an efficient way. In old computers buses were able to carry only on

Byte of data but with the improvement in technology the busses present in todays

Computer can carry multiple bytes at one time thus improving the speed an

Performance of computers.

 Address Bus

An address bus carries address information. It is a set of wires similar to the

Data by but it only connects central processing unit (CPU) and memory. Whenever

The processor needs data from the memory, it places the address of data on the address

Bus. The address is carried to the memory where the data from the requested address

Is fetched and placed on the data bus. The data bus carries it to the processor.

The reason for the importance of address bus is that the number of lines in

The address bus determines the maximum number of memory addresses, if an address

Bus has 8 lines, the maximum number of memory locations that can be addressed

Are 28 256. Today’s computers have 32 bit address lines so they can access

4GB (Giga Byte) of memory.

Control Bus

The control bus carries control information from the control unit to the other

Units. The control information is used for directing the activities of all units. The

Control unit directs the transfer of data to the ALU from the memory. This data is

The functioning of other

Units e.g. . Input/output devices, secondary storage etc.,

Computer Storage

Computer storage is also referred to as computer memory. Computer

IS used to store programs and data, There are two types of computer memory.

  • Main Storage or Main Memory
  • Secondary Storage or Secondary Memory

Main memory is accessible directly by the processing unit. RAM is an

Example of main memory. As soon as the computer is switched off the contents of the

Memory are lost you can store and retrieve data much faster with main memory

Compared to secondary memory, the reason is that the main memory is present on

Mother board. Secondary memory such as floppy disks, magnetic disk. Etc. is

Located outside the motherboard. Main memory is more expensive than secondary

Memory. That is why the size of main memory is less than that of secondary memory.

As the storage capacity of the main memory is limited and often it is

Necessary to store hundreds of millions of bytes of data for the CPU to process,

2-refore, additional memory is required in all the computer systems. This memory is

Secondary memory or secondary storage.

Input / Output Devices

A computer is only useful when it is able to communicate with the external

Environment. When we work with the computer, we feed data and instructions

Sough some devices to the computer. These devices are called input devices,

Similarly computer, after processing data and instructions, gives output through some

Devices called output devices. Input/output devices •are also known as peripheral



A port can be defined as a socket that enables an external device such as a

26nter to be attached to the computer”, All communication between a computer and

External devices is the result of properly connected ports. On every computer, a port’s

Connectors are attached to a motherboard. There are three basic types of ports:

  • Serial port
  • Parallel port
  • USB (Universal Serial Bus) port

‘Today’s computers have all these types of ports with each type doing a different




Serial port

A serial port allows a serial hardware device to communicate with th-

Computer by transmitting one bit of information at a time. Serial devices, such a

Mouse, modems, and keyboards, do not require fast data transmission rates. Serial

Ports often referred to as communications (COM) ports. It is an external port on thx

Back of the computer that attaches directly to the PC’s motherboard. These ports wer

One of the early ports put on computers. Older serial ports also used 25-pir

Connector for their serial port, but most new computers with serial ports feature onh

Nine pins.

Parallel ports

A parallel port lets an external parallel device communicate with the computer

by transmitting more bits (Such as 8 or 25) of data at a time there fore, it is much faster

Than a serial port. Most devices that send or receive large amounts of data, such as

Printers and scanners, use parallel ports. Parallel ports are often referred to as Line

Printer (LPT) ports. The parallel port is the largest port on the rear of your PC,

Comprising 25 lines that include 17 signal lines and eight ground lines.

USB Ports

USB (Universal Serial Bus) is€ a plug-and-play hardware interface for

Peripherals such as the keyboard, mouse, joystick, scanner, printer and modem. USB

Has a maximum bandwidth of 12 Mbits /sec and up to 127 devices can be attached.

With USB, a new device can be added to the computer without having to

Add an adapter card. It typically is located at the back PC and looks as in the following (sometimes positioned vertically). Sometimes it has the USB symbol next to it.









Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Check Also
Back to top button