C Program to Convert Binary to Hexadecimal

In this tutorial, we will learn about how to create a program in C that can convert any given binary number by user (at run-time) into its equivalent hexadecimal value. At last we have also created same purpose function-driven program that also converts binary number to hexadecimal number.

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

Binary Number
Hexadecimal Number
Binary to Hexadecimal Conversion Process

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

Binary to Hexadecimal in C

The question is, Write a program in C that converts binary number to hexadecimal. The answer to this question is:

#include<stdio.h>
#include<conio.h>
int main()
{
    int binnum, hex=0, mul=1, count=1, rem, i=0;
    char hexnum[20];
    printf("Enter any Binary Number: ");
    scanf("%d", &binnum);
    while(binnum!=0)
    {
        rem = binnum%10;
        hex = hex + (rem*mul);
        if(count%4==0)
        {
            if(hex<10)
                hexnum[i] = hex+48;
            else
                hexnum[i] = hex+55;
            mul = 1;
            hex = 0;
            count = 1;
            i++;
        }
        else
        {
            mul = mul*2;
            count++;
        }
        binnum = binnum/10;
    }
    if(count!=1)
        hexnum[i] = hex+48;
    if(count==1)
        i--;
    printf("\nEquivalent Hexadecimal Value = ");
    for(i=i; i>=0; i--)
        printf("%c", hexnum[i]);
    getch();
    return 0;
}

As the above program was written under Code::Blocks IDE, therefore after successful build and run, you will get the following output on your output screen. This is the first snapshot of the sample run:

c program to convert binary to hexadecimal

Now supply any binary number say 1101110 and press ENTER key to see its equivalent hexadecimal value as shown in the second snapshot of the sample run given below:

Here is the final snapshot of above program's another sample run:

Program Explained

Receive any binary number from user at run-time say 1101
Create a while loop that runs until the value of given binary number becomes 0
That is, at first run of the while loop, the condition binnum!=0 or 1101!=0 evaluates to be true, therefore program flow goes inside the loop
And binnum%10 or 1101%10 or 1 gets initialized to rem, then hex + (rem*mul) (we have initialized hex and mul with 0 and 1 at start of the program) or 0 + (1*1) or 1 gets initialized to hex
Now we have created a if block in such way, that the value of hex gets initialized to hexnum[] character array as hexadecimal digit one by one in corresponding to each 4-pair of binary digit.
Therefore, as at first run of the while loop, the condition of if statement, that is count%4==0 (we have initialized the variable count with 1 at start of the program) or 1%4== evaluates to be false, therefore program flow goes inside the else block of if statement, and there mul*2 or 1*2 or 2 gets initialized to mul, and the value of count variable gets incremented and becomes 2.
At last, binnum/10 or 1101/10 or 110 gets initialized to binnum, and then the program flow goes back to the condition of while loop
There again binnum!=0 or 110!=0 evaluates to be true, and the program flow again goes inside the while loop
And binnum%10 or 110%10 or 0 gets initialized to rem, then hex + (rem*mul) or 1 + (0*2) or 1 gets initialized to hex
Now the condition of if block, that is count%4==0 or 2%4== evaluates to be false, and the program flow goes inside the else block, and mul*2 or 2*2 or 4 gets initialized to mul, and the value of count gets incremented and becomes 3
At last, binnum/10 or 110/10 or 11 gets initialized to binnum, and then the program flow goes back to the condition of while loop
There again binnum!=0 or 11!=0 evaluates to be true, and the program flow again goes inside the while loop
And binnum%10 or 11%10 or 1 gets initialized to rem, then hex + (rem*mul) or 1 + (1*4) or 5 gets initialized to hex
Now the condition of if block, that is count%4==0 or 3%4== evaluates to be false, and the program flow goes inside the else block, and mul*2 or 4*2 or 8 gets initialized to mul, and the value of count gets incremented and becomes 4
At last, binnum/10 or 11/10 or 1 gets initialized to binnum, and then the program flow goes back to the condition of while loop
There again binnum!=0 or 1!=0 evaluates to be true, and the program flow again goes inside the while loop
And binnum%10 or 1%10 or 1 gets initialized to rem, then hex + (rem*mul) or 5 + (1*8) or 13 gets initialized to hex
Now the condition of if block that is count%4==0 or 4%4== evaluates to be true, therefore the program flow goes inside the if block this time, and as the value of hex (13) is not less than 10, therefore hex+55 or 13+55 or 68 (68 is the ASCII code for C) gets initialized to hexnum[i] (we have initialized the variable i with 0 at start of the program) or hexnum[0], and then 1, 0, and 1 gets initialized to mul, hex and count respectively. And the value of i gets incremented and becomes 1
At last, binnum/10 or 1/10 or 0 gets initialized to binnum, and the program flow goes back to the condition of the while loop
There, binnum!=0 or 0!=0 evaluates to be false, and the program flow does not goes inside the loop this time, that is the program flow goes out from the loop or exits from the loop, and then the condition count!=1 or 1!=1 evaluates to be false, therefore the program flow does not goes inside the if block.
Now the condition of the second if block, that is count==1 or 1==1 evaluates to be true, therefore the value of i gets decremented by 1, and becomes 0.
Now we have created the for loop that runs from the current value of i to 0
And print the value of each and every hexadecimal digit one by one, from last index to the first one
Here we have used ASCII code for the number and characters, that is 0, 1, 2, 3, ..., 7, 8, 9, A, B, C, D, E, F
That is, the ASCII code for 0, 1, 2, ..., 8, 9 are 48, 49, 50, ..., 56, 57. And the ASCII code for A, B, C, .., E, F are 65, 66, 67, ..., 69, 70
Therefore, if the value of hex is 0, then 0+48 (the ASCII code of 0) gets initialized to hexnum[], in same way if the value of hex is 13, then as 13 is greater than 10, therefore 13+55 or 68 (the ASCII code for C) gets initialized to hexnum[]

Binary to Hexadecimal in C using User-defined Function

Here is another program using user-defined function named BinToHex() that also does the same job, that is to convert any binary number to hexadecimal number.

Here, we have declared the variable i and the character array hexnum[] as global to make it known in both the function, that is main() and BinToHex().

#include<stdio.h>
#include<conio.h>
void BinToHex(int bin);
int i=0;
char hexnum[20];
int main()
{
    int binnum;
    printf("Enter any Binary Number: ");
    scanf("%d", &binnum);
    BinToHex(binnum);
    printf("\nEquivalent Hexadecimal Value = ");
    for(i=i; i>=0; i--)
        printf("%c", hexnum[i]);
    getch();
    return 0;
}
void BinToHex(int bin)
{
    int hex=0, mul=1, count=1, rem;
    while(bin!=0)
    {
        rem = bin%10;
        hex = hex + (rem*mul);
        if(count%4==0)
        {
            if(hex<10)
                hexnum[i] = hex+48;
            else
                hexnum[i] = hex+55;
            mul = 1;
            hex = 0;
            count = 1;
            i++;
        }
        else
        {
            mul = mul*2;
            count++;
        }
        bin = bin/10;
    }
    if(count!=1)
        hexnum[i] = hex+48;
    if(count==1)
        i--;
}

Here is the final snapshot of the above program's sample run:

Same Program in Other Languages

C Online Test

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