Algorithm to generate a random number? Don't use System.Random

Had there been no System.Rando开发者_如何学运维m class, how would have you generated a random number?

Are there any known algorithms or have you guys ever designed one?

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True random numbers can only be generated "outside" a computer, using radioactivity counts and such. Some VIA processors have hardware to do so.

Volume two of The Art of Computer Programming by Don Knuth spends a lot of time discussing exhaustively various pseudo-random number implementations from a mathematical background. Recommended reading.

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You can't really generate a truly random number with our current deterministic computers. There are, however, many different ways to generate pseudorandom numbers. See pseudorandom number generator on wikipedia for some information on the algorithms.

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Take a look at the Mersenne Twister. I belive this is the same algorithm implemented by System.Random, it is very common non cryptographically secure PRNG with a good random distribution.

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Like the other answers say, its not possible to generate true random numbers with a computer, but as for pseudo-random, one algorithm that I've used before is the Linear Congruential Generator, its simple and fast, but I'm sure there are much better alternatives.

Edit: Grammar