I think you know program for factorial right
i am giving example for one implement it using for loop and dynamic variable.

int i=2000,r=500;
float ncr;
int sub=n-r;
int fact=1;
for(int x=1;x<=i;x++)
{
fact=fact*x;
}
int nfact=fact;
for(int x=1;x<=r;x++)
{
fact=fact*x;
}
int rfact=fact;
ncr=nfact/(sub*rfact);