Simple pseudo random algorithm from The C Programming Language Pg 46.

46.c

//This next variable could be declared in a seperate file if you wanted to. Not neccesary, its just a global
unsigned long int next;

int rand(void){
    	//extern because I like to be explicit about my constants
	extern unsigned long int next;
	next = next * 1103515245 + 12345;
	return (unsigned int)(next/65536) % 32768;
}

void srand(unsigned int seed){
	next = seed;
}

#include <stdio.h>

main(){
	srand(13453461);
	int i;
	for(i=0; i < 10; ++i){
		printf("This is random number number %d: %d\n",i, rand());
	}
}