THE WHATIS.COM WORD-OF-THE-DAY September 13, 2001 pseudo-random number generator ______________ TODAY'S SPONSOR: **STORAGE DECISIONS FREE CONFERENCE** Storage Decisions brings together top storage analysts like Gartner's VP Nick Allen and Steve Duplessie of ESG and expert technologists like best-selling author Jon William Toigo. This exclusive conference is FREE to members who qualify. Apply today. http://ad.doubleclick.net/clk;3177364;5058249;p?http://www.StorageDecisions2001.com _____________ TODAY'S WORD: pseudo-random number generator See our definition with hyperlinks at http://whatis.techtarget.com/definition/0,,sid9_gci769541,00.html 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 algorithms 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. 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 numbers 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 21/2 or 101/2) 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 nth digit. 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 and because it is impossible to travel to infinity and find out, the matter becomes philosophical. RELATED TERMS algorithm http://searchvb.techtarget.com/sDefinition/0,,sid8_gci211545,00.html irrational number http://whatis.techtarget.com/definition/0,,sid9_gci283983,00.html logarithm http://whatis.techtarget.com/definition/0,,sid9_gci213698,00.html ___________________ SELECTED LINKS [1] Taygeta Scientific has links to several information sources and to some PRNGs. http://www.taygeta.com/random.xml _________________________ ASK THE EXPERT Dear Ask the Expert, I finished my Windows 2000 classes but I've been putting off taking my certification exams. I've heard that the exams are really hard and my own fear of failure is paralyzing me. How can I get myself to go take the exams? Is there any particular one I should start with? See expert Ed Tittel's answer: http://searchwin2000.techtarget.com/ateQuestionNResponse/0,289625,sid1_cid412676_tax285126,00.html _________________________ RECENT ADDITIONS [1] vi http://searchsolaris.techtarget.com/sDefinition/0,,sid12_gci768734,00.html [2] transparent computing http://whatis.techtarget.com/definition/0,,sid9_gci765426,00.html [3] transparent http://whatis.techtarget.com/definition/0,,sid9_gci765434,00.html [4] alphanumeric http://whatis.techtarget.com/definition/0,,sid9_gci763592,00.html [5] magnetic field strength http://whatis.techtarget.com/definition/0,,sid9_gci763586,00.html ======================================================== If you would like to sponsor this or any techtarget newsletter, please contact Gabrielle DeRussy at [EMAIL PROTECTED] ======================================================== If you no longer wish to receive this newsletter simply reply to this message with "REMOVE" in the subject line. Or, visit http://WhatIs.techtarget.com/register and adjust your subscriptions accordingly. If you choose to unsubscribe using our automated processing, you must send the "REMOVE" request from the email account to which this newsletter was delivered. Please allow 24 hours for your "REMOVE" request to be processed.
