C Exercises: Convert binary number to octal

C For Loop: Exercise-53 with Solution

Write a C program to convert a binary number to octal.

This C program converts a binary number to its equivalent octal representation. It prompts the user to input a binary number, then iterates through each digit to calculate its decimal equivalent. Afterward, it converts the decimal number obtained to octal format, storing and printing both the original binary number and its octal equivalent.

Visual Presentation:

Convert binary number to octal

Sample Solution:

C Code:

int main() {
    // Declare variables
    int n1, n, p = 1;
    int dec = 0, i = 0, d;
    int ocno = 0, dn;
    // Print output headers
    printf("\n\nConvert Binary to Octal:\n ");
    // Get binary input
    printf("Input a binary number: ");
    scanf("%d", &n);
    // Store input number
    n1 = n;
    // Convert binary to decimal
    // Loop through each binary digit
    while (n > 0) {
        // Get current digit
        d = n % 10;
        // Add digit * power of 2 to result
        dec += d * pow(2, i);
        // Increment power
        // Divide binary number
        n = n / 10;
    // Convert decimal to octal
    dn = dec; // Store decimal number
    i = 1;    // Reset power
    // Repeatedly divide decimal by 8
    while (dec > 0) {
        // Get remainder and add to result
        ocno += (dec % 8) * i;
        // Update power of 8
        i = i * 10;
        // Divide decimal number
        dec = dec / 8;
    // Print binary and octal result
    printf("\nThe Binary Number: %d\nThe equivalent Octal Number: %d\n\n", n1, ocno);
    return 0;


Convert Binary to Octal:                                                                                      
Input a binary number :1001                                                                                   
The Binary Number : 1001                                                                                      
The equivalent Octal  Number : 11 


Here's a brief explanation.

  • Header and Declarations:
    • Includes the necessary header files ('stdio.h' for input/output and 'math.h' for mathematical functions).
    • Declare variables 'n1' (input binary number), 'n' (temporary variable for input processing), 'p' (power of 2 multiplier), 'dec' (resulting decimal number), 'd' (temporary variable for digit extraction), 'ocno' (resulting octal number), 'dn' (backup of decimal number), i (loop variable).
  • User input:
    • Asks the user to input a binary number.
    • Reads the input and stores it in the variable 'n'.
  • Binary to Decimal Conversion (using a for loop):
    • Iterates through each binary number digit using a "for" loop.
    • Extracts the current digit and calculates its contribution to the decimal number using the 'pow' function.
    • Accumulates the result in the variable 'dec'.
  • Convert Decimal to Octal (using a for loop):
    • Initialize 'ocno' to 0 and i to 1 for the octal conversion.
    • Repeatedly divides the decimal number ('dec') by 8 using a "for" loop.
    • Calculates the remainder and adds it to the octal result ('ocno').
    • Update the power of 8 (i).
    • Continue until the decimal number becomes 0.
  • Result Display:
    • Prints the input binary number and its equivalent octal number.
  • Return Statement:
    • Returns 0 to indicate successful execution.

Flowchart :

Flowchart : Convert binary number into octal

C Programming Code Editor:

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