is a number randomly selected from distribution . This is based on the inverse transform sampling. For example, the inverse of cumulative Gaussian distribution with an ideal uniform PRNG with range (0, 1) as input would produce a sequence of (positive only) values with a Gaussian distribution; however When using practical number representations, the infinite "tails" of the distribution have to be truncated to finite values. Repetitive recalculation of should be reduced by means such as ziggurat algorithm for faster generation. Similar considerations apply to generating other non-uniform distributions such as Rayleigh and Poisson. See also List of pseudorandom number generators Applications of randomness Low-discrepancy sequence Pseudorandom binary sequence Pseudorandom noise Pseudorandom number Random number generation Random number generator attack Randomness Statistical randomness References Bibliography Barker E., Kelsey J., Recommendation for Random Number Generation Using Deterministic Random Bit Generators, NIST SP800-90A, January 2012 Brent R.P., "Some long-period random number generators using shifts and xors", ANZIAM Journal, 2007; 48:C188–C202 Gentle J.E. (2003), Random Number Generation and Monte Carlo Methods, Springer. Hörmann W., Leydold J., Derflinger G. (2004, 2011), Automatic Nonuniform Random Variate Generation, Springer-Verlag. Knuth D.E. The Art of Computer Programming, Volume 2: Seminumerical Algorithms, Third Edition. Addison-Wesley, 1997. . Chapter 3. [Extensive coverage of statistical tests for non-randomness.] Luby M., Pseudorandomness and Cryptographic Applications, Princeton Univ Press, 1996. von Neumann J., "Various techniques used in connection with random digits," in A.S. Householder, G.E. Forsythe, and H.H. Germond, eds., Monte Carlo Method, National Bureau of Standards Applied Mathematics Series, 12 (Washington, D.C.: U.S. Government Printing Office, 1951): 36–38. Press W.H., Teukolsky S.A., Vetterling W.T., Flannery B.P. (2007), Numerical Recipes (Cambridge University Press). Viega J., "Practical Random Number Generation in Software", in Proc. 19th Annual Computer Security Applications Conference, Dec. 2003. External links TestU01: A free, state-of-the-art (GPL) C++ Random Number Test Suite. DieHarder: A free (GPL) C Random Number Test Suite. "Generating random numbers" (in embedded systems) by Eric Uner (2004) "Analysis of the Linux Random Number Generator" by Zvi Gutterman, Benny Pinkas, and Tzachy Reinman (2006) "Better pseudorandom generators" by Parikshit Gopalan, Raghu Meka, Omer Reingold, Luca Trevisan, and Salil Vadhan (Microsoft Research, 2012) by Stephan Lavavej (Microsoft, 2013) Wsphynx a simple online random number generator.Random number are generated by Javascript pseudorandom number generators (PRNGs) algorithms