C Program to Convert Decimal to Binary using Bitwise AND operator

#include<stdio.h>
#include<conio.h>

void main()
{
unsigned int mask;
clrscr();
printf("Memory Required : %d butes",sizeof(mask));
getch();
}

Output :

Memory Required : 2 bytes

Above program is just to know the size of integer variable in C Programming (Borland C/C++ Compiler.) Integer number can be represented by 16 bits.

To convert the Decimal Number into Binary , Check First MSB bit of number , if it is 1 then display ’1′ otherwise display ’0′.

Program :

#include<stdio.h>
#include<conio.h>

void binary(unsigned int);   // Prototype Declaration

void main()
{
unsigned int num;
printf("Enter Decimal Number : ");
scanf("%u",&num);
binary(num);   // Function Call
getch();
}
//========================================================
void binary(unsigned int num)
{
unsigned int mask=32768;   //mask = [1000 0000 0000 0000]
printf("Binary Eqivalent : ");

while(mask > 0)
   {
   if((num & mask) == 0 )
         printf("0");
   else
         printf("1");
  mask = mask >> 1 ;  // Right Shift
   }
}

Output :

Enter Decimal Number : 10
Binary Eqivalent : 0000000000001010

Explanation of Decimal to Binary Program :

In this program we have accepted the decimal number using following lines -

printf("Enter Decimal Number : ");
scanf("%u",&num);

Inside the function we have initialized mask variable with 32768.

unsigned int mask = 32768;

i.e Binary representation of the number is 1000 0000 0000 0000

mask = 1000 0000 0000 0000

Now inside iteration we need to follow same steps : If result of mask is Zero then Print 0 else Print 1.

if((num & mask) == 0 )
         printf("0");
   else
         printf("1");

Consider the first iteration Masking will be like this -

1000 0000 0000 0000
0000 0000 0000 1010 &
----------------------
0000 0000 0000 0000

Now right shift mask by 1 so that new mask variable will contain following value -

0100 0000 0000 0000 - (Decimal Equivalent : 16384)

As mask variable is not equal to 0 so once again while loop will be executed and in the next iteration of while loop following numbers will be ANDed.

0100 0000 0000 0000
0000 0000 0000 1010 &
----------------------
0000 0000 0000 0000

Similarly, In each iteration we are shifting mask variable by 1 to right and ANDing the mask with number.

Algorithm for Decimal to Binary using Bitwise Operator :

1. Initialize ‘mask’ variable with 32768 [1000 0000 0000 0000]
2. Perform ANDing of two number’s (i.e Given variable and  Mask variable )
3. Check whether the Result of ANDing is 0 or not , if Yes Display 0 otherwise Display 1
4. Right shift mask variable by 1 [0100 0000 0000 0000]
5. Now check for Second bit , whether it is 0 or 1
6. Goto step 3 until ‘mask’ becomes Zero  [ 0000 0000 0000 0000 ]

Why We are right shifting Mask Variable ?

We have kept given number as it is but in each iteration we have right shifted given number by 1 and masked it with original number. Main purpose of doing this is to check bit status of all the bits of given number.

In the 13th iteration mask variable will be -

Mask Variable : 0000 0000 0000 1000
Num  Variable : 0000 0000 0000 1010  &
--------------------------------------
Result of AND : 0000 0000 0000 1000