Example: Reading and writing bits (generic version)

The six bitwise operators:

/* Desktop program - illustrating the use of bitwise operators */
#include <stdio.h>
void Display_Byte(const unsigned char);
/* ............................................................... */


int main()
{
unsigned char x = 0xFE;
unsigned int y = 0x0A0B;
printf("%-35s","x");
Display_Byte(x);
printf("%-35s","1s complement [~x]");
Display_Byte(~x);
printf("%-35s","Bitwise AND [x & 0x0f]");
Display_Byte(x & 0x0f);
printf("%-35s","Bitwise OR [x | 0x0f]");
Display_Byte(x | 0x0f);
printf("%-35s","Bitwise XOR [x ^ 0x0f]");
Display_Byte(x ^ 0x0f);
printf("%-35s","Left shift, 1 place [x <<= 1] ");
Display_Byte(x <<= 1);
x = 0xfe; /* Return x to original value */
printf("%-35s","Right shift, 4 places [x >>= 4]");
Display_Byte(x >>= 4);
printf("\n\n");
printf("%-35s","Display MS byte of unsigned int y");
Display_Byte((unsigned char) (y >> 8));
printf("%-35s","Display LS byte of unsigned int y");
Display_Byte((unsigned char) (y & 0xFF));
return 0;
}
COPYRIGHT ©MICHAEL J. PONT, 2001-2006. Contains material from:
Pont, M.J. (2002) “Embedded C”, Addison-Wesley.
PES I - 53
/* --------------------------------------------------------------- */
void Display_Byte(const unsigned char CH)
{
unsigned char i, c = CH;
unsigned char Mask = 1 << 7;
for (i = 1; i <= 8; i++)
{
putchar(c & Mask ? '1' : '0');
c <<= 1;
}
putchar('\n');
}