C - Mask to select multiple bits from a variable.

Introduction

The following code sets a value in a variable and then uses the bitwise operators to reverse the sequence of hexadecimal digits.

Demo

#include <stdio.h>

int main(void)
{
  unsigned int original = 0xDEAD;
  unsigned int result = 0;
  unsigned int mask = 0xF;          // Rightmost four bits

  printf("\n original = %X", original);

  // Insert first digit in result
  result |= original & mask;        // Put right 4 bits from original in result

                    // Get second digit
  original >>= 4;                   // Shift original right four positions
  result <<= 4;                     // Make room for next digit
  result |= original & mask;        // Put right 4 bits from original in result

    /* Get third digit */
  original >>= 4;                   // Shift original right four positions
  result <<= 4;                     // Make room for next digit
  result |= original & mask;        // Put right 4 bits from original in result

  printf("\t result = %X\n", result);
  return 0;/*  w ww.  j  a v  a 2  s. com*/
}

Result

Related Topic

• Bitwise Operators
• Using Bitwise Operators to check mask flag
• Displaying binary values
• Using the bitwise | operator
• Use binary OR operator to change character case
• Using bitwise &
• Operating exclusively with XOR
• ~ (complement) and ! (not) operators

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