Analog computer vs. digital computer: what is the difference?

A fundamental decision that is made when designing a computer is choosing whether it will be working on a digital or an analog system. But what exactly does this mean and what is the difference between these two types of computers? Keep reading to find out.

Difference between analog and digital computer

While digital computers work with discrete numeric or character variables, analog computers are designed to handle continuous streams of incoming data. Today, digital computers have a significantly wider range of application, while the analog ones are still used for only special purposes.

Examples of analog computers are slide rule, astrolabe, oscilloscope, television, analog sound processor, autopilot and a human brain. The most complex of such systems is the supercomputer.

What is an analog computer?

An analog computer a computing system which represents numerical data using analog physical variables (speed, length, voltage, current, pressure); this is also its main difference from the digital computer.

Types of analog computer:

Mechanical
Pneumatic
Hydraulic
Electromechanical
Electronic

The representation of mechanical analog computers is, for example, the number of turns of the gears of the mechanism. In the electric ones, differences in voltage are used. They can perform operations such as addition, subtraction, multiplication, division, differentiation, integration and inversion.

When working, analog computers simulate the process of computation, and the characteristics representing digital data are constantly changing with time.

The results of the work performed by analog computers are either graphically depicted on paper or on the screen of an oscilloscope, or an electrical signal which is used to control a process or operating mechanism.

These computers are perfectly suited for the realization of automatic control of production processes because they instantly react to various changes in the input data. Such computers are widely used in scientific research. For example, in the sciences where inexpensive electrical or mechanical devices are capable of simulating the studied situation.

In some cases, analog computers may be used for solving problems when there is no need to worry about the accuracy of the calculations. For example, electronic analog computers perform the implementation of tasks where solving differential equations, integration or differentiation are required. For each of these operations, special schemes and nodes are used, typically with the use of operational amplifiers. The integration is also easy to implement in hydraulic analog machines.

Examples of when they can be used

Analog computers work based on the assignment of the physical characteristics of their constituents. This is usually done by a method of inclusion/exclusion of certain elements of the circuits that connect these elements with wires and changing the settings of variable resistances, capacitances and inductances in the circuits.

Automotive automatic transmission is an example of a hydromechanical analog computer, where changing the torque of the fluid in the hydraulic actuator changes the pressure, which allows obtaining the desired result.

In addition to technical applications (automatic transmission, music synthesizer), analog computers are used to solve specific computational problems of a practical nature.

What is a digital computer?

A digital computer is intended for the transmission, storage and processing of information.

Currently, the phrase "electronic computing machine" has been eliminated from general use. The abbreviation "ECM" is used mainly as a legal term in legal documents and while talking in the historical sense, as well as to mean computer technology in 1940-80-ies.

By using computing power, the computer is able to process information according to a specific algorithm. Every task for a computer is a sequence of calculations.

Physically, the computer can function by moving mechanical parts, electrons, photons, quantum particles or by the use of effects of any other physical phenomena.

The design of the computers may directly model the problem to be solved as close as possible (in the sense of mathematical description) and reflect the studied physical phenomenon. Thus, the electron flows can be used as models of water flow through a simulation of levees or dams. Similarly constructed analog computers were common in the 1960-ies, but today they have become quite rare.

In most modern computers, tasks are first described in a commonly understood form (in this case all necessary information is typically represented in binary form — in the form of ones and zeros, although there were computers which used the ternary numeral system), then the steps for processing are reduced to application of the simple algebra of logic. Since almost all areas of mathematics can be reduced to the implementation of Boolean operations, a sufficiently fast electronic computer can be used to solve most math problems and most tasks of processing information which can be reduced to mathematical ones.

The results of the executed tasks can be presented to a user using various devices of input and output of the information, such as lamp indicators, monitors, printers, projectors, etc.

Common users and children often have difficulty accepting the idea that a computer is just a machine and it cannot "think" or "understand" the words it shows. Mechanical computers display only specified programs, points, lines, and colors with the help of input-output. The human brain then recognizes certain images, numbers, and words and gives them a certain value. More precisely, the main difference between a computer and human brain is in their capacity to think abstractly, and only the human brain has this ability. This includes creativity, imagination, reflection, independent study, aesthetic appreciation, etc.

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