Thursday, 30 April 2015

Classification of Computers

Computers differ based on their data processing abilities. They are classified according to purpose, data handling and functionality.

According to purpose, computers are either general purpose or specific purpose. General purpose computers are designed to perform a range of tasks.

They have the ability to store numerous programs, but lack in speed and efficiency. Specific purpose computers are designed to handle a specific problem or to perform a specific task. A set of instructions is built into the machine.

According to data handling, computers are analog, digital or hybrid. Analog computers work on the principle of measuring, in which the measurements obtained are translated into data. Modern analog computers usually employ electrical parameters, such as voltages, resistances or currents, to represent the quantities being manipulated. Such computers do not deal directly with the numbers. They measure continuous physical magnitudes. Digital computers are those that operate with information, numerical or otherwise, represented in a digital form. Such computers process data into a digital value (in 0s and 1s). They give the results with more accuracy and at a faster rate. Hybrid computers incorporate the measuring feature of an analog computer and counting feature of a digital computer. For computational purposes, these computers use analog components and for storage, digital memories are used.

According to functionality, computers are classified as :

Analog Computers

Analog computers are used to process analog data. Analog data is of continuous nature and which is not discrete or separate. Such type of data includes temperature, pressure, speed weight, voltage, depth etc. These quantities are continuous and having an infinite variety of values.

It measures continuous changes in some physical quantity e.g. The Speedometer of a car measures speed, the change of temperature

is measured by a Thermometer, the weight is measured by Weights machine. These computers are ideal in situations where data can be accepted directly from measuring instrument without having to convert it into numbers or codes.

Analog computers are the first computers being developed and provided the basis for the development of the modern digital computers. Analog computers are widely used for certain specialized engineering and scientific applications, for calculation and measurement of analog quantities. They are frequently used to control process such as those found in oil refinery where flow and temperature measurements are important. They are used for example in paper making and in chemical industry. Analog computers do not require any storage capability because they measure and compare quantities in a single operation. Output from an analog computer is generally in the form of readings on a series of dial (Speedometer of a car) or a graph on strip chart.

Digital Computers

A Digital Computer, as its name implies, works with digits to represent numerals, letters or other special symbols. Digital Computers operate on inputs which are ON-OFF type and its output is also in the form of ON-OFF signal. Normally, an ON is represented by a 1 and an OFF is represented by a 0. So we can say that digital computers process information which is based on the presence or the absence of an electrical charge or we prefer to say a binary 1 or 0.

A digital computer can be used to process numeric as well as non-numeric data. It can perform arithmetic operations like addition, subtraction, multiplication and division and also logical operations. Most of the computers available today are digital computers. The most common examples of digital computers are accounting machines and calculators.

The results of digital computers are more accurate than the results of analog computers. Analog computers are faster than digital. Analog computers lack memory whereas digital computers store information. We can say that digital computers count and analog computers measures.

Hybrid Computers

A hybrid is a combination of digital and analog computers. It combines the best features of both types of computers, i-e. It has the speed of analog computer and the memory and accuracy of digital computer. Hybrid computers are used mainly in specialized applications where both kinds of data need to be processed. Therefore, they help the user, to process both continuous and discrete data. For example a petrol pump contains a processor that converts fuel flow measurements into quantity and price values. In hospital Intensive Care Unit (ICU), an analog device is used which measures patient's blood pressure and temperature etc, which are then converted and displayed in the form of digits. Hybrid computers for example are used for scientific calculations, in defense and radar systems.


A minicomputer is a type of computer that possesses most of the features and capabilities of a large computer but is smaller in physical size.

A minicomputer fills the space between the mainframe and microcomputer, and is smaller than the former but larger than the latter. Minicomputers are mainly used as small or midrange servers operating business and scientific applications. However, the use of the term minicomputer has diminished and has merged with servers.

A minicomputer may also be called a mid-range computer.

Minicomputers emerged in the mid-1960s and were first developed by IBM Corporation. They were primarily designed for business applications and services that require the performance and efficiency of mainframe computers. Minicomputers are generally used as mid-range servers, where they can operate mid-sized software applications and support numerous users simultaneously.Minicomputers may contain one or more processors, support multiprocessing and tasking, and are generally resilient to high workloads. Although they are smaller than mainframe or supercomputers, minicomputers are more powerful than personal computers and workstations.


A microcomputer is a complete computer on a smaller scale and is generally a synonym for the more common term, personal computer or PC , a computer designed for an individual. A microcomputer contains a microprocessor (a central processing unit on a microchip ),memory in the form of read-only memory and random access memory , I/O ports and a busor system of interconnecting wires, housed in a unit that is usually called a motherboard .

A microcomputer is a standard
desktop computer used at a
home and in business.
Minicomputers are mid-sized
computer used in universities,
research labs and small corporations.
A microcomputer is a computer
with a microprocessor as its CPU.
Minicomputers are faster than
They are cheap, compact and can
be easily accommodated on a
study table.
They are expensive and larger than
Microcomputer is a single-user
Minicomputer is a multi-user
The two most common types of
storage devices used with
microcomputers are tapes and
For secondary storage, most
minicomputers use magnetic disks
or tapes.
Microcomputer is not powerful
or as fast as minicomputer
Minicomputer is powerful than
microcomputer but not as super
computer and mainframe computer.
Examples are- Modern computers
like desktop, laptop etc.
Examples are- IBM 9375,
Motorola 68040 etc.

Mainframe computers (colloquially referred to as "big iron") are computers used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning and transaction processing.
The term originally referred to the large cabinets called "main frames" that housed the central processing unit and main memory of early computers. Later, the term was used to distinguish high-end commercial machines from less powerful units. Most large-scale computer system architectures were established in the 1960s, but continue to evolve.
Modern mainframes can run multiple different instances of operating systems at the same time. This technique of virtual machines allows applications to run as if they were on physically distinct computers. In this role, a single mainframe can replace higher-functioning hardware services available to conventional servers. While mainframes pioneered this capability, virtualization is now available on most families of computer systems, though not always to the same degree or level of sophistication.


Difference between mini and main frame computers

Main frame computers are large scale general purpose computers systems. The word main frame has its origin in early computers which were big in size and required large frame work in house. Main frame computers have large storage capacities in several million words. Secondary storage devices are directly accessible by these computers. These computers systems have more than one CPU and can support a large number of terminals.

These computers are fast in operations and accept all types of high level languages.
Mini computers are general purpose computer system with reduced storage capacity and performance as compare to main frame computers. These computers operate a CPU speed of few million instructions per second. These computers accept all types of high level languages and word length in these computers is 16 or 32 bits. These computers can support more than 20 terminals.

Micro computers are available are small in size which utilize micro processors. The CPU of micro computers is usually contained in one chip. Micro computers have low storage capacity and slow operation rate than mini computers and main frame computers. Micro computers are provided with video display unit, printer and secondary storage devices such as CD Drive, hard disk.


The fastest type of computer. Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations. For example, weather forecasting requires a supercomputer. Other uses of supercomputers include animated graphics, fluid dynamic calculations, nuclear energy research, and petroleum exploration.
The chief difference between a supercomputer and a mainframe is that a supercomputer channels all its power into executing a few programs as fast as possible, whereas a mainframe uses its power to execute many programs concurrently.


Top Supercomputers-India is an effort to list the most powerful supercomputers in India. It is supported by Supercomputer Education and Research Centre, Indian Institute of Science , Bangalore. This effort is complementary to the Top500 project that lists the top 500 supercomputers in the world.

Top Supercomputers-India can help the Indian installation sites to compare their supercomputing capabilities with their counterparts in India. The project is meant to create and promote healthy competition among the supercomputing initiatives in India and can substantially lead to significant supercomputing advancement in the nation.


PARAM is a series of supercomputers designed and assembled by the Centre for Development of Advanced Computing (C-DAC) in Pune, India. The latest machine in the series is the PARAM Yuva II.

Advanced Numerical Research and Analysis Group

Advanced NUmerical Research and Analysis Group (ANURAG) is a laboratory of the Defence Research and Development Organisation (DRDO). Located in Kanchanbagh, Hyderabad, it is involved in the development of computing solutions for numerical analysis and their use in other DRDO projects.