aman-1998 / generating-random-numbers-using-c-language Goto Github PK

Generating-random-numbers-using-C-Language:-

The rand function, declared in stdlib.h, returns a random integer in the range 0 to RAND_MAX (inclusive) every time you call it. On machines using the GNU C library RAND_MAX is equal to INT_MAX or 231-1, but it may be as small as 32767. There are no particularly strong guarantees about the quality of random numbers that rand returns, but it should be good enough for casual use, and has the advantage that as part of the C standard you can assume it is present almost everywhere.

Note that rand is a pseudorandom number generator: the sequence of values it returns is predictable if you know its starting state (and is still predictable from past values in the sequence even if you don't know the starting state, if you are clever enough).

If you want to get different sequences, you need to seed the random number generator using srand i.e., srand(time(NULL)).

Here time(NULL) returns the number of seconds since the epoch (00:00:00 UTC, January 1, 1970, for POSIX systems, not counting leap seconds). Note that this still might give repeated values if you run it twice in the same second, and it's extremely dangerous if you expect to distribute your code to a lot of people who want different results, since two of your users are likely to run it twice in the same second.