Right method for activating internal pull-up resistors

Using Arduino General Electronics
4

Just for interest, INPUT_PULLUP does it in the order: set-input-mode, set-pin-high:

	} else if (mode == INPUT_PULLUP) {
		uint8_t oldSREG = SREG;
                cli();
		*reg &= ~bit;        // set to INPUT
		*out |= bit;         // output HIGH
		SREG = oldSREG;

Comments added by me.