What is pseudo-random number generator (PRNG)? - Definition from WhatIs.com


pseudo-random number generator (PRNG)

Part of the Mathematics glossary:

A pseudo-random number generator (PRNG) is a program written for, and used in, probability and statistics applications when large quantities of random digits are needed. Most of these programs produce endless strings of single-digit numbers, usually in base 10, known as the decimal system. When large samples of pseudo-random numbers are taken, each of the 10 digits in the set {0,1,2,3,4,5,6,7,8,9} occurs with equal frequency, even though they are not evenly distributed in the sequence.

Many algorithm s have been developed in an attempt to produce truly random sequences of numbers, endless strings of digits in which it is theoretically impossible to predict the next digit in the sequence based on the digits up to a given point. But the very existence of the algorithm, no matter how sophisticated, means that the next digit can be predicted! This has given rise to the term pseudo-random for such machine-generated strings of digits. They are equivalent to random-number sequences for most applications, but they are not truly random according to the rigorous definition.

The digits in the decimal expansions of irrational number s such as pi (the ratio of a circle's circumference to its diameter in a Euclidean plane), e (the natural- logarithm base), or the square roots of numbers that are not perfect squares (such as 2 1/2 or 10 1/2 ) are believed by some mathematicians to be truly random. But computers can be programmed to expand such numbers to thousands, millions, billions, or trillions of decimal places; sequences can be selected that begin with digits far to the right of the decimal (radix) point, or that use every second, third, fourth, or n th digit. However, again, the existence of an algorithm to determine the digits in such numbers is used by some theoreticians to argue that even these single-digit number sequences are pseudo-random, and not truly random. The question then becomes, Is the algorithm accurate (that is, random) to infinity, or not? -- and because no one can answer such a question definitively because it is impossible to travel to infinity and find out, the matter becomes philosophical.

This was last updated in March 2011
Contributor(s): bOiler
Posted by: Margaret Rouse

Related Terms


  • data-driven decision management (DDDM)

    - Data-driven decision management (DDDM) is an approach to business governance that values actions that can be backed up with verifiable data. The success of a data-driven approach is reliant upon th... (WhatIs.com)

  • continuum

    - A continuum is a continuous system or range in which adjacent elements do not vary from each other in any marked degree although the endpoints of the system may be drastically different. (WhatIs.com)

  • space

    - In mathematics, space is an unbounded continuum (unbroken set of points) in which exactly three numerical coordinates are necessary to uniquely define the location of any particular point. It is so... (WhatIs.com)


  • Mathematics

    - Terms related to mathematics, including definitions about logic, algorithms and computations and mathematical terms used in computer science and business.

  • Internet applications

    - This WhatIs.com glossary contains terms related to Internet applications, including definitions about Software as a Service (SaaS) delivery models and words and phrases about web sites, e-commerce ...

Ask a Question About pseudo-random number generator (PRNG)Powered by ITKnowledgeExchange.com

Get answers from your peers on your most technical challenges

Tech TalkComment



    Contribute to the conversation

    All fields are required. Comments will appear at the bottom of the article.