prime number from User defined f(x) in C.

#include<stdio.h>
int prime(int);
int main()
{
	int a,res,count=0;
	printf("Enter any number:\t");
	scanf("%d",&a);
	
	res=prime(a);
	    if(count==2)
	printf("\nPrime number"); 
	
     	else
	printf("\nNOT A PRIME NUMBER");
	
}
int prime(int a)
{
	int b,i,count=0;
	for(i=1;i<=a;i++)
	{
		b=a%i;
	}
	if(b==0)
	{
		count++;
	}
	
}