Example:

#include <stdio.h>

#define TOGGLE(PIN,N) (PIN ^=  (1<<N))

int main(){
	
	unsigned char val = 0x11;
	unsigned char bit = 2;
	
	printf("val = %X\n",val);
	
	//TOGGLE bit number 2
	TOGGLE(val, bit);
	printf("Aftre toggle bit %d first  time, val = %X\n", bit, val);

	//TOGGLE bit number 2 again
	TOGGLE(val, bit);
	printf("Aftre toggle bit %d second time, val = %X\n", bit, val);
	
	return 0;	
}

Output

    val = 11
    Aftre toggle bit 2 first  time, val = 15
    Aftre toggle bit 2 second time, val = 11

Explanation:

• Initially val is 0x11, its binary value is "0001 0001".
• In this example, we are toggling bit number 2 (i.e. third bit of the val), initially bit 2 is 0, after calling TOGGLE(val, bit) first time, the bit 2 will be 1. Hence, the value of val will be "0001 0100" – thus, the output will be 0x15 in Hexadecimal.
• Now, the bit 2 is 1, after calling TOGGLE(val, bit) again, bit 2 will be 0 again, hence the value of val will be "0001 0001" – thus, the output will be 0x11 in Hexadecimal.