C Programming Examples Tutorial Index

C Number Programs

This tutorial will guide you through writing a C program that converts an octal number (base 8) to its binary (base 2) equivalent. This is a fundamental concept in computer science, especially in digital systems where different number systems are often used.

What is Octal to Binary Conversion?

Octal to binary conversion transforms a number expressed in the octal number system (base 8) into the binary number system (base 2). In the octal system, numbers are represented using digits ranging from 0 to 7, while the binary system uses only two digits, 0 and 1.

Algorithm for Octal to Binary Conversion

  1. Initialize Variables: Declare variables to store the octal number, the binary equivalent, and a temporary variable.
  2. Input Octal Number: Prompt the user to enter an octal number. Use scanf() to take the input.
  3. Conversion Process:
    • For each digit of the octal number, convert it to a 3-digit binary number.
    • Append these binary sequences to form the complete binary number.
  4. Output Binary Number: Display the final binary number using printf().

Code Example

#include <stdio.h>

int main() {
    int octal, binary = 0, decimal = 0, base = 1;
    int octalDigit, tempDecimal;

    // Input octal number
    printf("Enter an octal number: ");
    scanf("%d", &octal);

    // Octal to Decimal conversion
    while (octal != 0) {
        octalDigit = octal % 10;
        decimal += octalDigit * base;
        octal /= 10;
        base *= 8;

    base = 1;

    // Decimal to Binary conversion
    while (decimal != 0) {
        tempDecimal = decimal % 2;
        binary += tempDecimal * base;
        decimal /= 2;
        base *= 10;

    // Display the binary number
    printf("Binary equivalent: %d\n", binary);

    return 0;

Program Output:

For example, if you input the octal number 123, the program will convert and display the binary equivalent.

Enter an octal number: 123
Binary equivalent: 1010011


This tutorial guided you on creating a C program that converts octal numbers to binary. Understanding different number systems like this is crucial for working in computing fields such as computer architecture and digital electronics.

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