On the basis of principle of construction, computers are divided into three types: Analog, Digital and Hybrid computers.
- Analog Computers
- Digital Computers
- Hybrid Computers
An analog computer is a form of computer that uses the continuously changeable aspects of physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved. Mechanical analog computers very very important in gun fire control in World War II. They were made in significant numbers. Analog computers were also used in science and industry.
Analog quantities show the continuity of a specified value. An example is a thermometer because it measures the length of a mercury column, which varies continuously. Another example is analog clock, which measures time by means of the distance traveled by the hand of the clock around a dial.
A digital computer is an electronic computing machine that uses the binary digits (bits) 0 and 1 to represent all forms of information internally in digital form. Every computer has a set of instruction that define the basic functions it can perform. Sequences of these instructions constitute machine language programs that can be stored in the computer and used to tailor it to an essentially unlimited number of specialized applications. Calculators are small computers specialized for mathematical computations. General-purpose computers range from pocket-sized personal digital assistants (notepad computers), to medium-sized desktop computers (Personal computers and workstations), to large powerful computers that are shared by many users via a computers network. The vast majority of digital computers now in used are inexpensive. Special-purpose microcontrollers that are embedded often invisibility, in such devices as toys, consumer electronic equipment, and automobiles are also the examples of digital computers.
Differences between Analog and Digital Computers
Analog computers works with continuous values.
It has very limited memory.
It has no state.
It can perform certain types of calculations.
It is difficult to use.
analog computer is used in engineering and scientific applications.
Analog computer is used for calculations and measurements of physical quantities such as weight, height, temperature and speed.
Its accuracy is high.
Its readability is low.
Examples of analog computers are thermometer, analog clock, and older weighing machines.
Digital computer works with discrete values. It can work only with digits.
It can store large amount of data.
It has two states ON and OFF
Its speed of calculation is very high.
It is easy to use.
Digital computer is widely used in almost all fields of life.
Digital computer is used to calculate mathematical and logical operations.
Its accuracy is comparatively low.
Its readability is high.
Examples of digital computers are digital watches, digital weighing machines, mini computers, microcomputers, mainframe and supercomputers.
Hybrid computers are computers that exhibit features of analog computers and digital computers. The digital component normally serves as the controller and provides logical operations, while the analog component normally serves as a solver of differential equations. An example of a hybrid computer system is a cement plant where all calculations are made by digital systems and accordingly actions such as increase of certain material in the furnace and increase / decrease of fuel for temperature is performed by the help of analog system. another example is ICU (Intensive Care Unit) of hospital where hybrid computer is used. Analog quality of these computers controls the temperature of the room and digital quality informs the doctors about the blood pressure, temperature and physical status of the patient.