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Advanced Programming Techniques in C

Masks and Their Construction

Explore techniques for constructing bit masks in C to manipulate specific bits with AND, OR, and XOR operations. Understand how to use hexadecimal values and the BV macro for clear and efficient bit setting.

We'll cover the following...

Creating mask values

Suppose n = 45 and your task is to:

  • AND it with a number whose 3rd bit is on
  • OR it with a number whose 7th bit is on
  • XOR it with a number whose 4th bit is on

The original number is n; the second operand is known as a mask. Here, we intend to learn how to create mask values.

Example program 1: Creating mask values using a hexadecimal number

See the code given below!

C
#include <stdio.h> 



int main( ) 

{

    // Initialize variables

	unsigned char n = 45 ; 

    unsigned x, y, z;

    // AND with number whose 3rd bit is ON

    x = n & 0x08;

    // OR with number whose 7th bit is ON

    y = n | 0x80;

    // XOR with number whose 4th bit is ON

    z = n ^ 0x10;

    // Display x, y, and z

	printf ( "%d\n", x ) ; 

    printf ( "%d\n", y ) ; 

    printf ( "%d\n", z ) ; 

}

Line 9: The mask in which 3rd3^{rd} ...