The C standard library function int rand(void) returns a pseudo random integer between 0 and RAND_MAX (which should be at least 2^15, depending on the actual implementation).

Depending on the distribution of the pseudo random numbers, it will be true for over > 99% of its applications.

Source: trust me bro, and C++ reference

Furthermore, there is no integer between 0 and 1, but I guess you mean a real number between 0 and 1.