RAND_MAX

From cppreference.com
< c‎ | numeric‎ | random
Defined in header <stdlib.h>
#define RAND_MAX /*implementation defined*/

Expands to an integer constant expression equal to the maximum value returned by the function rand(). This value is implementation dependent. It's guaranteed that this value is at least 32767.

[edit] See also

generates a pseudo-random number
(function)
seeds pseudo-random number generator
(function)
C++ documentation for RAND_MAX