C program to convert Decimal to Binary number system

Write a C program to input decimal number from user and convert to binary number system. How to convert from decimal number to binary number system in C program. Logic to convert decimal to binary number system in C programming.

Input decimal number: 112

Binary number: 0111000

Required knowledge

Basic C programming, While loop, String

Decimal number system

Decimal number system is a base 10 number system. Decimal number system uses only 10 symbols to represent all number i.e. 0123456789

Binary number system

Binary number system is a base 2 number system. Binary number system uses only 2 symbols to represent all numbers i.e. 0 and 1

Algorithm to convert from decimal to binary

Algorithm Decimal to Binary conversion
begin:
read (decimal);
binary ← 0; place ← 1; rem ← 0;
while (decimal > 0) do 
begin 
    rem ← decimal % 2;
    binary ← (rem * place) + binary;
    place ← place * 10;
    decimal ← decimal / 2;
end
write('Binary = ' binary)
end

Program to convert decimal to binary number system

/**
 * C program to convert from Decimal to Binary number system
 */

#include <stdio.h>

int main()
{
    long long decimal, tempDecimal, binary;
    int rem, place = 1;

    binary = 0;

    /* Input decimal number from user */
    printf("Enter any decimal number: ");
    scanf("%lld", &decimal);
    tempDecimal = decimal;

    /* Decimal to binary conversion */
    while(tempDecimal > 0)
    {
        rem = tempDecimal % 2;

        binary = (rem * place) + binary;

        tempDecimal /= 2;

        place *= 10;
    }

    printf("Decimal number = %lld\n", decimal);
    printf("Binary number = %lld", binary);

    return 0;
}

Note: The above program converts the decimal to binary number only up to 18 binary bits. Use the below program to convert from decimal to binary number for a higher range.

Program to convert decimal to binary more than 18 bits

/**
 * C program to convert from Decimal to Binary number system
 */

#include <stdio.h>
#include <string.h>

int main()
{
    long decimal, tempDecimal;
    char binary[65];
    int index = 0;
    
    /* Input decimal number from user */
    printf("Enter any decimal value : ");
    scanf("%ld", &decimal);
    
    /* Copy decimal value to temp variable */
    tempDecimal = decimal;
    
    while(tempDecimal > 0)
    {
        binary[index] = (tempDecimal % 2) + '0';
        
        tempDecimal /= 2;

        index++;
    }
    binary[index] = '\0';
    
    /* Reverse the converted binary to get final binary result */
    strrev(binary);

    printf("Decimal value = %ld\n", decimal);
    printf("Binary value of decimal = %s", binary);

    return 0;
}

Advance your C skills by learning this program using other approach.

Learn more – Program to convert decimal to binary using bitwise operator.

Enter any decimal value : 112
Decimal value = 112
Binary value of decimal = 01110000

Happy coding 😉