The function int rand(void); returns a pseudo random integer number between 0 and RAND_MAX. RAND_MAX is a constant defined in stdlib standard library, it's value is library dependent, but is guaranteed to be at least 32767. The function rand uses a seed to generate the series, which should be initialize using srand. If seed remains the same, then rand function generates same sequence of random numbers.
- In range of 0 - N : rand() % N+1.
- In range of 1 - N : (rand() % N) + 1.
- In range of N - M : (rand() % M-N+1) + N.
Function prototype of rand
int rand(void);
Return value of rand
This function returns an integer between 0 and RAND_MAX.
C program using rand function
The following program shows the use of rand function to generate a sequence of pseudo random numbers.
#include <stdio.h>
#include <stdlib.h>
int main(){
unsigned int seed;
int n, counter;
printf("Enter a unsigned number(seed)\n");
scanf("%u", &seed);
/* Initialize random number generator using srand */
srand(seed);
printf("Enter number of random numbers\n");
scanf("%d", &n);
for(counter=0; counter < n; counter++){
printf("%d ", rand());
}
return 0;
}
Output
Enter a unsigned number(seed) 234 Enter number of random numbers 7 802 32478 7150 29924 30401 13148 15783