C program to generate random numbers
C program to generate pseudo-random numbers using rand and random function (Turbo C compiler only). As the random numbers are generated by an algorithm used in a function they are pseudo-random, this is the reason that word pseudo is used. Function rand() returns a pseudo-random number between 0 and RAND_MAX. RAND_MAX is a constant which is platform-dependent and equals the maximum value returned by rand function.
C programming code using rand
We use modulus operator in our program. If you evaluate a % b where a and b are integers then result will always be less than b for any set of values of a and b. For example
For a = 1243 and b = 100
a % b = 1243 % 100 = 43
For a = 99 and b = 100
a % b = 99 % 100 = 99
For a = 1000 and b = 100
a % b = 1000 % 100 = 0
In our program we print pseudo random numbers in range [0, 100]. So we calculate rand() % 100 which will return a number in [0, 99] so we add 1 to get the desired range.
#include <stdio.h>
#include <stdlib.h>
int main() {
int c, n;
printf(“Ten random numbers in [1,100]\n“);
for (c = 1; c <= 10; c++) {
n = rand() % 100 + 1;
printf(“%d\n“, n);
}
return 0;
}
If you rerun this program, you will get the same set of numbers. To get different numbers every time you can use: srand(unsigned int seed) function; here seed is an unsigned integer. So you will need a different value of seed every time you run the program for that you can use current time which will always be different so you will get a different set of numbers. By default, seed = 1 if you do not use srand function.
C programming code using random function (Turbo C compiler only)
Function randomize is used to initialize random number generator. If you don’t use it, then you will get same random numbers each time you run the program.
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
int main()
{
int n, max, num, c;
printf(“Enter the number of random numbers you want\n“);
scanf(“%d”, &n);
printf(“Enter the maximum value of random number\n“);
scanf(“%d”, &max);
printf(“%d random numbers from 0 to %d are:\n“, n, max);
randomize();
for (c = 1; c <= n; c++)
{
num = random(max);
printf(“%d\n“,num);
}
getch();
return 0;
}