how to randomly print 1 to 10 in C

Question

Possible Duplicates:
Generate Random numbers uniformly over entire range
In C, how do I get a specific range of numbers from rand()?

i want to generate random number in C. It has rand() and srand() function in stdlib.h But it gives me very large number. But I want only number b/w 1 to 10. So, is it possible and if yes then how? If is possible to generate character from a-z randomly.

Answer 1

The simplest way is to use the modulo operator to cut down the result to the range you want. Doing rand() % 10 will give you a number from 0 to 9, if you add 1 to it, i.e. 1 + (rand() % 10), you'll get a number from 1 to 10 (inclusive).

And before others complain, this may dilute the random distribution, nevertheless, it should work fine for simple purposes.

Answer 2

Modulo (%) has some bias in it.

Slightly preferred is to scale the random number:

int aDigit = (int) (((double)rand() / (RAND_MAX+1)) * 9 + 1);
printf("%d", aDigit);

Breaking it down:

((double)rand() / RAND_MAX)

will generate a double between 0.0 and 0.99999

* 10

turns that to a number 0.0 to 9.9999.

+ 1;

turns that into 1.0 - 10.999

(int)

turns that into 1-10, which is what you asked for.