Example:

#include <stdio.h>

#define SETPIN(PIN,N) (PIN &= ~(1<<N))

int main(){
	
	unsigned char val = 0xFF;
	unsigned char bit = 2;
	
	printf("val = %X\n",val);
	
	//SET bit number 2 to zero 
	SETPIN(val,bit);
	printf("Aftre setting  bit %d to zero, val = %X\n", bit, val);
	
	return 0;	
}

Output

    val = FF
    Aftre setting  bit 2 to zero, val = FB

Explanation:

• In this example, initially the value of val is 0xFF that is "1111 1111" in binary.
• To set bit number 2 (i.e. third bit) to zero, when we call macro SETPIN(val, bit), the bit number 2 will set to 0. Thus, the output will be "1111 1011" i.e. 0xFB in Hexadecimal.