Setting and clearing multiple register bits

Setting bits 

“`REG |= (1<TWCR |= (1<<TWEN) | (1<<TWIE) | (1<<TWEA);

Clearing

REG &= ~((1<<BIT1) | (1<<BIT2) | (1<<BIT3));

for example:

TWCR &= ~((1<<TWEN) | (1<<TWIE) | (1<<TWEA));