/*
  This example illustrates a couple of ways in which we can make use of bit manipulation operators.

  To compile: gcc -o 09-bits 09-bits.c -Wall
  To run: ./09-bits

  
  C. Andrews
  2016-03-04
*/

#include <stdio.h>

// #define is a way to _define_ values (or macros) that can be used in your code
// It is the recommended way to create constants
// here we are making bitmasks that represent different boolean states
#define LIKES_DW  1    // first bit
#define LIKES_BLACK 2  // second bit



int main(int argc, char * argv[]){

  short x = 593;

  // this illustrates using bit shifting and masking (ANDing to a value with 1s in the position we are interested in) to extract individual bytes out of a number
  printf("%#x : %#x   %#x\n",x,  (x >> 8) & 0xff, x & 0xff);


  // we extend this idea to loop through all of the bits of a number to see the binary representation
  // We start at the highest order bit
  // since this is a short, we have 16 bits, so we want to start by shifting over by 15 to get at that one bit
  for (int i = sizeof(x)*8-1; i >= 0; i--){
    
    // here is the shift and the mask
	  printf("%d", (x >> i)& 1);
    
    // to make this a little easier to compare to our hex, we insert spaces every four digits
	  if (i % 4 == 0){
	    printf(" ");
	  }
  }

  printf("\n");


  // example of creating a variable to hold a collection of boolean flags
  char flags = 0;
  
  // we can set the flags using the bitwise OR
  flags = LIKES_DW | LIKES_BLACK;

  // we can query the collection of flags by masking against the original value
  if (flags & LIKES_BLACK){
	  printf("likes black\n");
  }
  
  

  
  return 0 ;
}