Bit Manipulation 101

OR

pour mettre un bit a 1

X | 0 = X
X | 1 = 1

AND

pour mettre un bit a 0

X & 0 = 0
X & 1 = X

SNIPPETS

#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit)) 
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))

FLAG

uint8_t FLAGS = 0;

#define F_f1 0
#define F_f2 1
#define F_f3 2
#define F_f4 3

sbi(FLAGS,f1) //Set FLAG

if (FLAGS & _BV(F_f1)) //si flag ON

if (!(FLAGS & _BV(F_f2))) //si flag OFF

cbi(FLAGS,F_f1) //Clear Flag