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C Program to Convert Decimal to Binary



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In this tutorial, we will learn about how to create a program in C that converts any given number (in decimal number) by user at run-time into its equivalent value in binary number. At last we have also created a program that uses user-defined function to do the same job.

But before going through the program, if you are not aware of

then refer to Decimal to Binary conversion step by step process. Now let's move on to program.

Decimal to Binary in C

To convert decimal number to binary number in C programming, you have to ask from user to enter the number (in decimal number system) to convert it into binary number and then display the equivalent value in binary as output.

// Decimal to Binary in C
// ----codescracker.com----

#include<stdio.h>
#include<conio.h>
int main()
{
    int decnum, binnum[50], i=0;
    printf("Enter any decimal number: ");
    scanf("%d", &decnum);
    while(decnum!=0)
    {
        binnum[i] = decnum%2;
        i++;
        decnum = decnum/2;
    }
    printf("\nEquivalent Binary Value = ");
    for(i=(i-1); i>=0; i--)
        printf("%d", binnum[i]);
    getch();
    return 0;
}

As the above program was written under Code::Blocks IDE, therefore after successful build and run, here is the sample run. This is the first snapshot of the sample run:

c program convert decimal to binary

Now supply any number (in decimal) say 117 and press ENTER key to see its equivalent binary value as shown in the second snapshot of sample run given here:

decimal to binary in c

Program Explained

without using Array

The question is, write a program in C that converts decimal number to binary without using array. The answer to this question is given below:

// C Decimal to Binary without using Array
// ----codescracker.com----

#include<stdio.h>
#include<conio.h>
int main()
{
    int decnum, binnum=0, mul=1, rem;
    printf("Enter any decimal number: ");
    scanf("%d", &decnum);
    while(decnum>0)
    {
        rem = decnum%2;
        binnum = binnum+(rem*mul);
        mul = mul*10;
        decnum = decnum/2;
    }
    printf("\nEquivalent Binary Value = %d", binnum);
    getch();
    return 0;
}

This program produces the same output as of previous program.

without Modulous Operator

If you want to create the same program but without using modulous operator (%), then

The question is, Write a program in C that converts decimal to binary without using modulous operator. The answer to this question is:

// Decimal to Binary in C without Modulous Operator
// ----codescracker.com----

#include<stdio.h>
#include<conio.h>
int main()
{
    int decnum, binnum[50], i=0, temp, chk;
    printf("Enter any Decimal number: ");
    scanf("%d", &decnum);
    while(decnum!=0)
    {
        temp = decnum/2;
        chk = temp*2;
        if(chk==decnum)
            binnum[i] = 0;
        else
            binnum[i] = 1;
        i++;
        decnum = temp;
    }
    printf("\nEquivalent Binary Value = ");
    for(i=(i-1); i>=0; i--)
        printf("%d", binnum[i]);
    getch();
    return 0;
}

Here is the final snapshot of the sample run:

c decimal to binary without modulous

using User-Defined Function

Now let's create a user-defined function named DecToBin() that receives one argument (the decimal number) to convert and stores its equivalent binary value one by one to bin[] array as shown in the program given below. The question is, Write a program in C that converts Decimal number to Binary number using User-Defined Function. The answer to this question is:

// Decimal to Binary in C using Function
// ----codescracker.com----

#include<stdio.h>
#include<conio.h>
void DecToBin(int dec);
int bin[50];
static int i;
int main()
{
    int decnum;
    printf("Enter any decimal number: ");
    scanf("%d", &decnum);
    DecToBin(decnum);
    printf("\nEquivalent Binary Value = ");
    for(i=(i-1); i>=0; i--)
        printf("%d", bin[i]);
    getch();
    return 0;
}
void DecToBin(int dec)
{
    while(dec!=0)
    {
        bin[i] = dec%2;
        i++;
        dec = dec/2;
    }
}

Here is the final snapshot of the sample run:

c decimal to binary using function

Here we have declared the array bin[] and variable i outside the function main(), as after declaring both outside the main() function (at start of the program), the array (bin[]) and variable (i) both stays known and can be used throughout the program. The value of i is declared as static variable. Because static variable holds its previous value. And one more thing about static variable is that, if you will not initialize any value to a static variable initially, then it holds 0 as its initial value.

Same Program in Other Languages


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