msp430 launchpad sample code to blink LED 1

blink.c

//Demo app to blink the red LED (LED1) on the TI Launchpad
//which is attached to P1.0
//The green LED(LED2) is connected to P1.6

#include <msp430g2553.h>
 
int main(void) {
  volatile int i;
 
  // stop watchdog timer
  WDTCTL = WDTPW | WDTHOLD;
  // set up bit 0 of P1 as output
  P1DIR = 0x01;
  // intialize bit 0 of P1 to 0
  P1OUT = 0x00;
 
  // loop forever
  for (;;) {
    // toggle bit 0 of P1
    P1OUT ^= 0x01;
    // delay for a while
    for (i = 0; i < 0x6000; i++);
  }
}

//set up bit 0 of P1 as output
P1DIR = 0x01;

I didn't see any evidence that shows bit 0 of P1 is chosen
If I choose bit 2 or 3? What's the code look like?

0x01 is in hex, in binary that's 0000 0001. So, what the line:
P1DIR = 0x01;
is saying is set bit 0 in port 1 direction register high. This sets the P 1.0 to an output pin.

If you said something like 2 or 3 the code wouldn't run because you are trying to output on P 1.0.

TI actually makes this a little easier by defined all the bits in header file so for example you could write this:
P1DIR |= BIT0;
Instead of:
P1DIR = 0x01;

Can you pls give an idea regarding interfacing Bluetooth with msp430