What does the following code snippet do$?$

int gcd$($int a$,$ int b$)\{$

while $($b $!=0)\{$

int temp $=$ b;

a $=$ temp;

$\}$

return a;

$\}$

is it checks if a number is prime, calculates the factorial of a number, finds the square root of a number, or computes the greatest common divisor $($GCD$)$ of two numbers