What Is Computer? / Define Computer

Information Technology

What is Computer? / Define Computer.

A computer is anelectronic device which accepts and store input data, process them, and produce output results under the direction of a detailed stored program of instructions.

OR

It is an electronic device (machine) which accepts our input in the form of data, process this input and then displays output in the form of information.

OR

It is a device capable of performing a series of arithmetic or logical operations.

Parts of Computer

Virtually every computer may be divided into five (5) logical components

1. Input Unit
2. Central Processing Unit
3. Control Unit
4. Arithmetic/Logic Unit
5. Registers
6. Memory Unit
7. Output Unit

Following figure is stylized diagram of the basic components of a computer.

Input Unit

It is used to enter the data in computer’s main memory. There are several types of input devices also known as peripheral devices e.g. Keyboard, Mouse, Joystick, Scanner, Barcode reader, Mic etc. these devices perform following functions.

1. Accepts the data or instruction from the user.
2. Converts this data or instruction into computer acceptable form.
3. Supplies this converted data & instructions to the computer system for further processing.

Processing Unit

The processing unit is the most important and powerful part of computer system. It is the heart of computer system. All calculations and other operations are performed in this unit.

Functions of Processing Unit

• Accepts data or instructions from input unit and stores them in memory.
• Stores intermediate and final result of processing.
• Interprets (translate) or manipulate the instruction and send commands to relevant units.
• Does all arithmetic operations on the data i.e. addition, subtraction, multiplication, division etc.
• Does all logical and decision-making operations on data, i.e. comparison of data.
• Sends the result to the output devices when required.

Parts of Processing Unit

Processing unit is further divided into two parts.

1. Central Processing Unit (CPU)
2. Memory Unit

Central Processing Unit (CPU)

This is the major part of the computer and it controls all the activities of computer. It is also called brain of computer system.

It is further divided into three parts:

1. Control Unit (CU)
2. Arithmetic and Logic Unit (ALU)
3. Memory (Registers).

1.Control Unit (CU)

It is the most important part of the CPU. It controls and coordinates the activities of all other units.

2.Arithmetic Logic Unit (ALU)

All the arithmetical and logical activities are performed in the ALU. It is the place where all calculations are performed and all decisions are made.

3.Registers/Memory

The processor contains special storage locations called registers. These are temporary storage devices and all the data is temporarily stored in them before and after processing.

Memory Unit(MU):-

This is the storage device where the data and instructions fed by the user are stored.

The computer memory is classified into

• Main memory: This is the place where the data and instructions supplied by the input devices are stored.

It consists of RAM (Random Access Memory) a temporary memory and ROM (Read Only Memory).

• Secondary memory: This is the permanent memory and also called as back up memory. It stores a large about of information for a long time.

• Cache memory: This is the high speed memory and placed between the CPU and the main memory. Users cannot access it.

Basic Units of Data Storage

There are three basic units of data storage called bit, byte and nibble.

Bit

Bit is an abbreviation of two words Binary Digit. It is smallest storage unit of the computer memory. A bit may have any of two values i.e. 0 or 1. 0 is used for off state whereas 1 is used for on state.

Nibble

Nibble is larger then bit but smaller then Byte. It is combination of four bits.

Byte

Next to nibble is a byte. It is a combination of eight bits or two nibbles. It is used to store a single alphanumeric character (i.e. any digit from 0-9 or an alphabet from A-Z or a-z or any special symbol like / ? , + - * etc).

Some commercial units of data storage that are composed of bytes are described in the table below

Output Unit

Output unit is used to display the results of processing. E.g. Printers, Monitors, plotters etc.Output devices perform following functions.

• Accepts the results produced by the computer in coded form.
• Converts these coded results into the human readable form using a device known as output interface.
• Supplies the converted results to the outside world.

Components of Computer

The computer is divided into two major components Hardware and Software. These two components are combined to form a complete functional system called computer.

Hardware

All the computer devices are called Hardware. For example Input devices, memory, processor, ports, buses, cables, connectors, output devices, networking devices are all examples of hardware.

Software

All the computer programs are called Software. For example: Operating Systems (Windows, DOS, and Linux), programming languages (C, C++ Java, VB), application packages( MS-Word, Excel, games etc) are the examples of software.

It is further divided into two categories namely System Software’s (Packages) and Application Software’s.

System Software

It is used to run and monitor computer hardware e.g. operating system which controls the functionalities and manages all the resources of computer system also provides user-friendly environment to the users.

Application Software

It is designed for specific purpose and cannot be used everywhere. For example MS Office, Accounting software’s, games, etc.

What is the Difference between Data & Information?

Data:

All the facts and figures entered in the computer are called Data.

Information:

The Processed data is called information.

Q.Explain the different types of computers.

Digital Computer

Based on technology Analog Computer

Hybrid computer

TYPES OF COMPUTERS

Micro computer

Mini computer

Computers for Main frame computer

organization

Super computer

l. Computers based on technology-

• Digital computer:-Computers that works on digital data such as 0’s and 1’s

E.g. (Personal Digital ComputerAssistant)

• Analog computer:-They accept data whose values keep changing with respect to time.

Data may be in the form of continuous voltages, frequencies, temperature etc.

Processing is done on continuously varying signals.

E.g. Speedometer

• Hybrid Computer:-It is designed to handle digital and analog data and hence also called analog-digital computer.

Accepts analog signals and converts into digital form.

2. Computers for organization:-

• Micro Computer:-It is powerful, easy maintenance, low cost computer It is the most common type of PC and commonly called as desktop. They are small in size and do not have large storage capacities. E.g.: PC,

• Mini computer:-Computers with capabilities intermediate of that between main frame and micro computers. It is used by small and mid-size business organizations.

• Main frame computer:-It is more powerful than micro computers. They have high processing speeds and can store large amounts of data. They are used in research organizations, large industries, and large business and government organizations. They consume more electricity

E.g.: IBM 3000 series, UNIVAC 1180

• Super computers:-Computers that are used for scientific and engineering applications. They can handle very large data bases or a great amount of data computation. They can perform one trillion operations per second. Used in the field of science and defense, designing and launching missiles, weather forecasting, biomedical research. E.g: CRAY-3, HITAC S-300

Q. What are the different kinds of memory used in computers? Explain with examples.

Volatile memory-RAM

Primary memory

Non-volatile memory-ROM

MEMORY

Secondary memory

Cache memory

Primary memory:

• The memory is accessible directly to the CPU of the computer.
• The memory is very fast.
• This allows the CPU to store and retrieve data quickly.
• Volatile memory: The memory that loses its contents when the computer is turned off.
• Since the CPU can read the data from the memory or can write the data into the memory they are also called as read-write memories.
• E g. RAM (Random Access Memory): It is possible to read and write the data into the memory. It is temporary memory.
• Non volatile memory: The memory that retains its contents even after the computer is turned off memory. They hold the data permanently.
• E.g. ROM (Read Only Memory): The information stored in it can be only be read.

Secondary Memory:

• It’s is the permanent memory which stores large amount of information for a long time
• It’s also called back up memory or auxiliary memory.
• It is connected to CPU and is made of magnetic material.
• E.g. Floppy disc, Hard Disk, CDs, Flash Memory etc

Cache memory:

• It’s a high speed memory and is placed between CPU and main memory.
• The data and instructions stored in it are accessed at a higher speed
• Users cannot access this memory
• It stores data and instructions that are currently to be executed

Q. What is software? What are the different types of software?

All the computer’s programs are called Software.

Application software

SOFTWARE

System software

Application software;-

• It tells the computer how to accomplish specific tasks, such as word processing or drawing for the user.
• Word processing software for creating text based documents
• Spreadsheet for creating numeric based documents such as budgets
• Database management software for building and manipulating large sets of data
• Presentation program for creating and presenting electronic slide shows
• Graphics program for designing illustrations or manipulating photographs, movies or animation
• Web design tools and web browsers
• Entertainment and education software
• Games

System software:-

• It is any program that controls the computer hardware or that can be used to maintain the computer in some way so that it runs more effectively.

Generations of Computer

The computers can be divided into five generations depending upon the technologies used. These generations differ in size and processing capacity.

The First Generation ofComputers (1948 — 1958)

The main features of this generation are:

1. Used vacuum tubes for circuitry
2. Used magnetic drums for memory
3. Used machine language to perform operations
4. Able to solve one problem at a time
5. Output consisted of punched cards or paper

Disadvantages of this generation were:

1. Very expensive to operate
2. Very large in size.
3. Generate lot of heat.
4. Heavy air-conditioning is required.
5. Less reliable.
6. Consume very high voltage.
7. Low storage capacity.

The Second Generation of Computers (1959 — 1967)

The main features of this generation are:

1. Used Assembly language instead of binary language.
2. Later on used High Level Languages like COBOL, FORTRAN BASIC and PL/I
3. More reliable then previous generation.
4. Smaller in size as compared to previous generation.
5. Produce less heat as compare to previous generation.
6. Less power consumption then previous generation.
7. High capacity of internal storage.
8. Used magnetic core technology
9. Stored instructions in memory

Disadvantages of this generation were:

1. Still require high air-conditioning.
2. Input and output devices were very slow.

2.8.1The Third Generation of Computers (1968 — 1973)

The main features of this generation are:

1. First commercial operating system of real time is introduced.
2. Smaller in size as compared to first two generations.
3. Keyboards, Monitors were used
4. Higher capacity internal storage.
5. Operating system is used to control the computer and its resources.
6. Remote communication facilities made possible.
7. Multiprogramming facilities.
8. Used High-Level Language (HLL), like RPG and Pascal.
9. Programs written for one computer were compatible with others.
10. High speed
11. Small in size.
12. Power consumption is low.
13. Weight has decreased.

The Fourth Generation ofComputers (1974 — 1982)

The main features of this generation are:

1. Contained entire CPU on a single silicon chip.
2. Very much reliable as compared to all previous generations.
3. Magnetic disks became the primary means of internal storage
4. Large internal storage capacity.
5. Single chip contains thousands of IC’s.
6. The size became very small due to the use of LSI (Large Scale Integrated) and VLSI (Very Large Scale Integrated) circuits.
7. Less expensive.
8. Very fast as compared to all previous generations.

The Fifth Generation ofComputers (1982 — Till now)

The main features of this generation are:

1. Automatic programming, computational logic and pattern recognition.
2. Able to execute billions of instructions per second.
3. Easy and natural to use with high intelligence and natural human input and output mechanism.
4. Reliable and efficient software development by new languages.
5. Improved functions and performance making computers smaller, faster, lighter and flexible.

Data processing:

Batch processing is execution of a series of programs ("jobs") on a computer without human interaction.

Batch processing has these benefits:

• It allows sharing of computer resources among many users.
• It makes best use of time & resources.
• It is used for efficient bulk database updates and automated transaction processing.

A popular computerized batch processing procedure is printing.

Interactive processing:is execution of a series of programs ("jobs") on a computer with input from human interaction.The opposite of batch processing.

Mohammad NaiyerPage 1