REGISTER = 0b11110000;
REGISTER = 0xF0;

REGISTER |= BITx; //turn bit x on
REGISTER |= BITx + BITy; //both on

REGISTER &= ~BITx; //turn bit x off
REGISTER &= ~(BITx +BITy); //both off

REGISTER ^= BITx; //toggle bit x
REGISTER ^= BITx + BITy; //toggle both

 1 #include "io430.h"
 2 
 3 void main(void)
 4 {
 5   // Stop watchdog timer to prevent time out reset
 6     WDTCTL = WDTPW + WDTHOLD;
 7 
 8     P1OUT = 0; //initialize the output state before changing the pin to an output
 9     P1DIR |= BIT0; //P1.0 output 0
10 
11     while(1)
12     {
13         //code...
14     }
15 
16 }

 1 #include "io430.h"
 2 
 3 #define PUSH2 BIT3
 4 
 5 void main( void )
 6 {
 7     // Stop watchdog timer to prevent time out reset
 8     WDTCTL = WDTPW + WDTHOLD;
 9 
10     P1OUT = 0;
11     P1OUT |= PUSH2; //initialize the pullup state
12     P1REN |= PUSH2; //enable internal pullup
13     P1DIR &= ~PUSH2; //set P1.3 to input mode (default)
14     //state on P1.3: (P1IN & PUSH2) == PUSH2
15 
16     while(1)
17     {
18         //code...
19     }
20   
21 }