C Etymology

bitwise-and-operator

&: integer × integer → integer

&: long × long → long

&: unsigned integer × unsigned integer → unsigned integer

&: unsigned long × unsigned long → unsigned long

bitwise-and-operator

For each bit position, the result is 0 iff either operand is 0.

For each bit position, the result is 1 iff both operands are 1.

For each bit position, the result is the boolean AND of the corresponding operand bits:

Boolean AND
Operands		Result
0	0	0
0	1	0
1	0	0
1	1	1

bitwise-and-operator

The bitwise and operators have no side effects.

bitwise-and-operator

The bitwise and operator is mathematically commutative.

bitwise-and-operator

The bitwise and operator associates syntactically left to right.

The bitwise and operator is mathematically associative.

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

void Display (short A, short B);
void ToBinary (char * Display, short N);

short main () {
  time_t T;
  srand (time (&T));
  Display (2, 7);
  Display (15, 22);
  Display (rand() - 16768, rand() - 16768);
  Display (rand() - 16768, rand() - 16768);
  return 0;
}

void Display (short I, short J) {
  char Binary [17];
  short K;
  K = I & J;
  ToBinary (Binary, I);
  printf ("   %6i  %s\n", I, Binary);
  ToBinary (Binary, J);
  printf ("&  %6i  %s\n", J, Binary);
  printf ("   ------  ----------------\n");
  ToBinary (Binary, K);
  printf ("   %6i  %s\n", K, Binary);
  printf ("   ======  ================\n\n");
}

void ToBinary (char * Display, short N) {
  short I;
  I = 15;
  while (I >= 0) {
    Display [I] = (N & 1) + '0';
    N >>= 1;
    --I;
  }
  Display [16] = 0;
}

        2  0000000000000010
&       7  0000000000000111
   ------  ----------------
        2  0000000000000010
   ======  ================

       15  0000000000001111
&      22  0000000000010110
   ------  ----------------
        6  0000000000000110
   ======  ================

    13302  0011001111110110
&   15714  0011110101100010
   ------  ----------------
    12642  0011000101100010
   ======  ================

   -13987  1100100101011101
&    9139  0010001110110011
   ------  ----------------
      273  0000000100010001
   ======  ================


    

#include <stdio.h>
#include <stdlib.h>

void Pack (int * Code, unsigned month, unsigned day, int year);
void Unpack (int Code, unsigned * Month, unsigned * Day, int * Year);

int main () {
  int year;
  unsigned month;
  unsigned day;
  int Packed;
  
  year = 1900 + (rand () % 200);
  month = 1 + rand () % 12;
  day = 1 + rand () % 28;
  
  printf ("Initial:  %i/%u/%u\n", month, day, year);
  Pack (&Packed, month, day, year);
  printf ("Packed:   %il\n", Packed);
  Unpack (Packed, &month, &day, &year);
  printf ("Unpacked: %i/%u/%u\n", month, day, year);
  
  return 0;
}

void Pack (int * Code, unsigned Month, unsigned Day, int Year) {
  *Code = Year << 9
         | (Month & 15) << 5 
         | (Day & 31);
}

void Unpack (int Code, unsigned * Month, unsigned * Day, int * Year) {
  *Year = Code >> 9;
  *Month = (Code >> 5) & 15;
  *Day = Code & 31;
}

Initial:  3/27/2030
Packed:   1039483l
Unpacked: 3/27/2030