Decimal to Binary in C

What is a decimal number?

A decimal number is a number represented in the decimal number system. This system of binary conversion uses base 10 to represent numbers, i.e. the digits in the list is one of the following numbers: 1, 2, 3, 4, 5, 6, 7, 8, 9, 0.

For Example: 12, 132, 45 etc.

What is a binary number?

A binary number is a number that is being represented in the binary number system. This system uses the base as 2 to represent numbers, i.e. each digit in a binary number is one of the following numbers: 0 or 1.

For Example: 1010, 1110, 1001 etc.

To convert a decimal number to binary, we should follow the following steps:

1. Divide the decimal number by 2.
2. Write down the remainder.
3. Divide the result from step 1 by 2.
4. Write down the remainder.
5. Repeat this process until the result of the division is 0.

For example, to convert the decimal number 15 to binary, we have followed the above steps like this:

1. 15 / 2 = 7 with a remainder of 1
2. 7 / 2 = 3 with a remainder of 1
3. 3 / 2 = 1 with a remainder of 1
4. 1 / 2 = 0 with a remainder of 1
5. So, the binary representation of 15 is 1111.

Here's an example in C that demonstrates how to implement this algorithm:

Example 1:

// convert decimal to binary


#include <stdio.h>
#include <math.h>


long long convert(int);


int main() {
  int n, bin;
  printf("Enter a decimal number: ");
  scanf("%d", &n);
  bin = convert(n);
  printf("%d in decimal =  %lld in binary", n, bin);
  return 0;
}


long long convert(int n) {
  long long bin = 0;
  int rem, i = 1;


  while (n!=0) {
    rem = n % 2;
    n /= 2;
    bin += rem * i;
    i *= 10;
  }


  return bin;
}

Output:

Enter a decimal number: 15
15 in decimal =  1111 in binary

Here’s another program explaining the same:

Example 2:

#include <stdio.h>
#include <math.h>
int main()


{


int num, i = 0, j;
int binary[100];


printf("Enter a decimal number: ");
scanf("%d", &num);


while (num> 0)
    {
binary[i] = num % 2;
num = num / 2;
i++;
    }


printf("Binary equivalent: ");


for (j = i - 1; j >= 0; j--)
printf("%d", binary[j]);


return 0;
}

Output:

Enter a decimal number: 25
Binary equivalent: 11001

Program Explanation:

Here, we can see that this example takes a decimal number as an argument and prints out its binary representation.

Decimal to binary using loop in C

Example 3:

#include <stdio.h>


void decToBinary(int n) 
{ 
int binaryNum[32]; 
int i = 0; 
while (n > 0) { 
binaryNum[i] = n % 2; 
        n = n / 2; 
i++; 
    } 
for (int j = i - 1; j >= 0; j--) 
printf("%d", binaryNum[j]); 
} 


int main() 


{ 
int n;
printf("Enter a decimal number: ");
scanf("%d", &n);
printf("Binary equivalent of %d is: ", n);
decToBinary(n);
return 0; 


}

Output:

Enter a decimal number: 25
Binary equivalent of 25 is: 11001

Program Explanation:

This program first defines a function decToBinary that takes an integer n as input and converts it to binary using a loop. It stores the remainder when n is divided by 2 in an array called binaryNum until n becomes 0. Then, it prints the array in reverse order to get the binary equivalent of the decimal number.

In the main function, the program prompts the user to enter a decimal number, reads it using scanf, and then calls the decToBinary function to convert it to binary and print the result.

Using Bitwise Operators:

Example 4:

#include <stdio.h>
void decToBinary(int n) 
{ 
for (int i = 10; i>= 0; i--) { 
int k = n >>i; 
if (k & 1) 
printf("1"); 
else
printf("0"); 
    } 
} 


int main() 
{ 
int n;
printf("Enter a decimal number: ");
scanf("%d", &n);
printf("Binary equivalent of %d is: ", n);
decToBinary(n);
return 0; 
}

Output:

Enter a decimal number: 25
Binary equivalent of 25 is: 00000011001

Program Explanation:

This program first defines a function decToBinary that takes an integer n as input and converts it to binary using bitwise operators. It uses a loop to iterate over the bits of n from the most significant bit (MSB) to the least significant bit (LSB). For each bit, it shifts n to the right by i bits and then ANDs it with 1 to check if the bit is set. If the bit is set, it prints 1, otherwise it prints 0.

In the main function, the program prompts the user to enter a decimal number, reads it using scanf, and then calls the decToBinary function to convert it to binary and print the result.