The Difference Between Digital & Analog Computers

Some users may not remember the days of analog computing.

You may have heard the term "analog computer" and wondered how it relates to digital computing. Both types of devices perform calculations and solve problems, but each uses a different method to accomplish those tasks. You may not be able to purchase an analog computer in a department store, but you can build one if you understand the technology.

Digital Computers and Binary Logic

Computers work by accepting data, processing it and doing something with the results. Enter two numbers using a keyboard, and a computer may add them and show you the sum, or store the result in a database. Computers that you work with daily are digital computers. They process data and perform calculations using binary numbers to perform calculations. A binary number consists of ones and zeros. The binary equivalent of five, for example, is 101. Each digit in a binary number represents a computer memory location called a bit. Bits in a digital computer can be on or off.

Analog Computers

Unlike digital computers, analog computers do not work with binary numbers. Instead, they model physical processes that occur in real life. An analog computer can work with an infinite number of irrational values that lay between any two numbers. An irrational number, such as Pi, is a number that you cannot express exactly. Because analog computers can work with these types of continuous values, they are useful for working with systems that involve voltages, frequencies, temperatures and other entities that can have non-discrete values. A typical analog computer, for example, may perform actions based on the depth of water in a vat or the output voltage of an electrical device at a moment in time.

Common Analog Device

A slide rule is an example of an analog computing device. This device allows you to work with variable data entities known as logarithms. Musicians often play electronic synthesizers that used analog computer technology. The popular Moog synthesizer, for instance, is a customizable device that allows different musicians to adjust settings to achieve a desired sound. A common thermometer is also an analog device, because its mercury indicator can respond to weather changes, and rise or fall depending on the current temperature.

Current Technology

Most computers are digital even though analog computers existed long before scientists invented digital computing. The military found analog computers useful in World War II. By the 1970s, digital computers became faster, more powerful and capable of managing more memory. This resulted in the decline of analog computer use, and they were slowly phased out in the late 1970s. Today's digital computers perform most computing tasks, from managing the Internet to controlling orbiting satellites. You can find old analog computers in museums and read about them in textbooks.

References

• California Institute of Technology: History of Recent Science and Technology: Apollo Guidance Computer History Project - Conference 4 - Interview with Richard Battin
• The University of New Mexico: Computer Terminology - Binary
• Alan Turing: A Brief History of Computing
• Perfecting Sound Forever: An Aural History of Recorded Music; Greg Milner - Google Books
• Concise Encyclopedia of Computer Science; Edwin D. Reilly - Google Books