C++ Programming/Code/Standard C Library/Functions/rand

rand edit

#include <cstdlib>
int rand( void );

The function rand() returns a pseudo-random integer between zero and RAND_MAX. An example:

srand( time(NULL) );
for( i = 0; i < 10; i++ )
  printf( "Random number #%d: %d\n", i, rand() );

The rand() function must be seeded before its first call with the srand() function - otherwise it will consistently return the same numbers when the program is restarted.

The generation of random numbers is essential to cryptography. Any stochastic process (generation of random numbers) simulated by a computer, however, is not truly random, but pseudorandom; that is, the randomness of a computer is not from random radioactive decay of an unstable chemical isotope, but from predefined stochastic process, this is why this function needs to be seeded.

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