Computers In General Can Be Classified into two major categories based upon following criteria
a) According to the logic used by the computer.
b) According to size of computer.
Classification as per the logic used by computer
Computers can be classified into various categories based upon logic used. They are:
a) Analog Computers
b) Digital Computers
c) Hybrid Computers
Analog Computers: These are the computers which operate on the principle of creating a physical analog of mathematical problems. These computers continuously measure physical variables. These computers use signals as input, which can come from devices like thermometers, speedometers, barometers etc. These signals are continuous flow of physical quantity, e.g. temperature, speed, pressure etc, which vary continuously. This result given by these computers usually is not very precise, accurate and consistent. Because of the nature of operation, their use is limited. Speedometer of a vehicle can be a good example of analog computers, where the aped varies continuously.
Digital Computers: These are the computers which accepts digits and alphabets as input, which a used for solving, controlling any problem which can be expressed mathematically. These computers take data in form of discrete signals representing ON (High) or Off (Low) voltage state of electricity. The data input can be represented as sets of 0’s and 1’s representing low and high respectively. Then computers convert data into discrete form before operating on it. Digital watches can be good example of digital computer, as the time which is displayed does not vary continuously but changes from one discrete value in the other. The term “computer” used in our day to day life is reference to the digital computer only. Digital computers can be further classified based upon:
a) Purpose of use.
b) Size and capabilities
Classification of digital computers as per the purpose of their use
a) General Purpose digital computers
b) Special Purpose digital computers
1. General purpose digital computers: These are those computers which can theoretically use for any type application. These computers can be used in solving a business problem as well mathematical equation with same accuracy and consistency. Most of the computers now are general purpose digital computers. All the PCs, which have become almost every household affair, are all general purpose digital computers.
2. Special purpose Digital Computers: These are those digital computers which are designed, made and used for any specific job. These are usually used for those purposes which are critical and need great accuracy and response like satellite launching, weather forecasting, ignition instruments etc.
Classification of digital computers according to the used of capabilities:
1. Super Computers
2. Mainframe Computers
3. Medium sized computers
4. Mini computers
5. Micro Computers
1. Super Computers: These are the computers which are characterized as being the fasted, with very high processing speeds, very large size, most powerful and most costly of all their cousins. These are used widely in complex scientific applications like processing geological data, genetic engineering etc. These computers recognize words up to length of 64 bits and more. Their speed of calculations is up to 1.2 billion instructions per second and they can take input from more than 1000 individual work stations. PARAM is an example of super computer developed in India.
2. Mainframe Computers: mainframe computers are a computer which has capability to support many peripheral devices and terminals, which can process several million instructions per second (MIPS), as well support more than 1000 remote systems. Mainframes are mostly used for systems like railway reservations etc.
3. Medium sized computers: These computers are mini versions of mainframe computers; they are relatively smaller than mainframe and have smaller power than mainframes. Their processing speeds are relatively high with support for about 200 remote systems.
4. Mini computers: These computes are relatively smaller and are less expensive than mainframe and medium sized, but they can if needed be portable in comparison with mainframes. They are relatively faster and it can support about 10-20 user terminals connected to it. These types of computers are generally easy to use. They can handle database, statically problems, accounting etc. using special software designed for above uses.
5. Micro Computers: These are the most widely used category of computers which we commonly term as personal computers (PCs). The word micro suggests only the size, but not the capacity. These computers can fit themselves on to a desk top. They are capable to do all input-output operations. They can also be connected to few peripheral devices.
As any hybrid, is a combination of best qualities of the available types, so that it becomes the best by adopting best qualities of given variety of objects? The same concept is adopted here. The hybrid computers are those computers which adopt the best qualities of both analog and digital computers, thus, becoming capable to work on analog or digital data. These computers are mostly used for automation of various complicated physical processes and machines.