4.Classification of Computers

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Classification of Computers



Anitha Padmanaban ACET

Introduction

Computers are broadly classified into

Based on Operating Principle

Based on applications

Based on size and capability




Based on Operating Principle

Based on operating principles, computers are

divided into

Analog Computers

Digital Computers

Hybrid Computers




Analog Computers

Represent data in the form of continuous

electrical signals having specific magnitude

Allows different operation to be performed atsame time

The electronic circuit used in analog computer is

Operational Amplifier (Op-Amp)

Op-Amp is made up of semiconductor

integrated circuits




Characteristic Feature of Analog

Computer

Large voltage gain

Voltage gain is defined as the ratio of the output voltage

to the input voltage

Infinite input resistance

Input resistance is defined as the ratio of change in input

voltage to the change in input current

Zero output resistance The output resistance is the nominal resistance

measured with no load




IC of an Op-Amp

Amplifier

Input Resistor Feedback

Resistor


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Analog Computers

Advantage

Very fast in their operation

Allows several operations to be carried out at the

same time

Powerful tool that solve differential equations

Disadvantage

Does not produce accurate results



Analog Computer



Digital Computer

Also known as digital information processing

Stores and processes data in digital form (0’s &

1’s)

Produce the output in digital form

Capable of processing analog data

Analog data is converted into digital data

Conversion of digital to analog data are done by

bulit-in function



Hardware Components

1. Arithmetic Logic Unit (ALU)

Performs various arithmetic operations like

Addition

Multiplication

Subtraction

Division

Logic operations like AND, OR, NOT



Hardware Components

2. Control Unit (CU)

Helps in directing the operations of ALU

3. Memory Unit (MU)

Stores data in temporary or permanent basis

4. Input Unit

Enter the data into the computer

5. Output Unit

Displays the information generated by the computer to

the user



Digital Computer

Advantage

Faster and more reliable

Can be used in home, colleges, universities, etc



Hybrid Computer

Combination of analog and digital computer

Data is measured and processed in the form of

electrical signals and stored with digitalcomponents

Can be used to perform various types of logical

operations

Accepts continuous input signals and convert

them into set of discrete values



Hybrid Computer

Advantage

Very fast

Efficient

Reliable

Less expensive than digital computers

Disadvantage

Cost –effective to perform complex operation

Applications Hospitals: to measure the heart beat of patient

Scientific applications, Engineering fields, Controlling business

processes



Based on Applications



Based on Applications General Purpose Computers

Works in all environments

Versatile

Can store number of programs

Not efficient

Consume large amount of time in generating result

Special Purpose Computers

Performs only specific function

Not versatile

Speed and memory size depend on the task to beperformed

Less expensive

Do not contain any redundant information

Efficient and consume less amount of time in



Based on Size and Capability



Size and Capability

Computers differ from each other in terms of shape, size and

weights

Each type of computer perform some unique functions

On the basis of size and capability, computers can be classified

into

Micro computer

Mini computer

Mainframe computer

Super computer



Micro Computer

Small and cheap digital computer

Hardware Components

Built around a microprocessor, a storage unit and an

I/O channel

Also contains power supply, connecting cables,

keyboard, mouse, printer and scanner

Software Components

Operating system, System software and Utility

software



Block Diagram of Micro

Computer

Microprocessor

Peripheral devices

Interface Circuitry

Memory

System Bus



Microprocessor

Heart of microcomputer

Incorporates all the functions of CPU on to a single IC

Basic units are

ALU

Perform various arithmetic operations

Register unit

Used to store the data and instructions temporarily needed by ALU

Includes Accumulator, Program Control, I/O, Instruction register,

Memory Address Register (MAR) and Memory Buffer Register

(MBR)

Control unit

Used to manage and direct operations performed by




Microprocessor

Depending on the size the microprocessor are

further classified into

Desktop computers

Laptop computers

Hand-held computers

Etc……




Memory Used to store the data and instructions

Two types of memory

Primary memory

Also called as main memory

Used to store data temporarily

Secondary memory

Also called as auxiliary memory

Used to store data permanently

Example

Magnetic disks, magnetic tapes, etc




Peripheral device

They are generally the input and output devices

The various input devices are

Keyboard and mouse

The various output devices are

Monitor and printer




System Bus

Also called as front side bus, memory bus, local

bus or host bus

Used to connect microprocessor, memory andperipheral device into a single unit




Mini Computers

First introduced by Digital Equipment Corporation in

1960

Smaller in size

Can handle more data and more input and output

More powerful than micro computer

Can support 4 to 200 users at same time

All desktop computers can be connected to a single mini

computer

Handle 1000s of transactions in a day




Main frame computers

Very large computer

Used for large scale business organizations

Capable of handling millions of records per day

Bigger and more expensive

Predecessor of servers

Occupies large space

Can maintain large databases

Also known as super servers or database servers




Characteristics of main frame computers

Maximum of 16 microprocessors

RAM storage lies between 128 MB and 8 GB

Run multiple operating system

Different cabinets for primary storage, secondary

storage and I/O units

Can handle huge amount of operations at the

same time




Super Computers

Fastest type of computer

Perform complex operations at a very high speed

Developed by Seymour Cray in 1960 at ControlData Corporation (CDC)

More expensive

Example: CRAY 3, Cyber 205, NEC SX-3 and

PARAM from India



Applications of Super Computers

Weather forecasting

Animated graphics

Fluid mechanics

Nuclear energy research

Petroleum exploration

4.Classification of Computers

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