How to manually generate random numbers [closed]

Question

I want to generate random numbers manually. I know that every language have the rand or random function, but I'm curious to know how this is working. Does anyone have code for that?

Answer 1

POSIX.1-2001 gives the following example of an implementation of rand() and srand(), possibly useful when one needs the same sequence on two different machines.

static unsigned long next = 1;
/* RAND_MAX assumed to be 32767 */
int myrand(void) {
    next = next * 1103515245 + 12345;
    return((unsigned)(next/65536) % 32768);
}
void mysrand(unsigned seed) {
    next = seed;
}

Answer 2

Have a look at the following:

Random Number Generation

Linear Congruential Generator - a popular approach also used in Java

List of Random Number Generators

And here's another link which elaborates on the use of LCG in Java's Random class