C Reference function rand() generate a random number

This function of stdlib will generate a random number.

Usage of rand():

int rand (void);


The function rand() returns a pseudo-random integral number.
This number will be in the range 0 to RAND_MAX. The algorithm of rand() uses a seed to generate the series of numbers, this is why srand must be used to initialize the seed to some distinctive value.

The constant RAND_MAX is defined in standard library (stdlib).

The random numbers are delivered from a predetermined range.

Return value:

Will return an integer value between 0 and RAND_MAX.

Source code example of rand():


	int main ()
		int number, input;
		/* initialize random seed: */
		srand ( time(NULL) );
		/* Generate a random number: */
		number = rand() % 10 + 1;
		do {
				printf ("Guess the number (1 to 10): ");
				scanf ("%d",&input);
				if (number > input)
					printf ("The number is higher\n");
			} while (number!=input);
		printf ("That is correct!\n");
		return 0;

This entry was posted in C Reference stdlib.h Functions. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site. Tweet This! Tweet This! or use to share this post with others.

There are currently 4 responses to “C Reference function rand() generate a random number”

Why not let us know what you think by adding your own comment!

  1. Tzrinz on October 28th, 2013:


  2. Aki on November 1st, 2013:

    Had the idea for 1-10 and thankfully yours is the only one i found that helped me

  3. nisha on December 11th, 2013:

    a C program to find the total number of
    students with Pass and Fail grades in a class
    of 35

    please can reply

  4. asdf on April 16th, 2014:

    nisha, if pass is 50marks and below that is fail then,this is the solution to count the passes and fails.

    int students,pass=0,fail=0;
    printf("Fail %d\n",fail);
    printf("Pass %d\n",pass);

Leave a Reply: