C Program to Convert Binary to Octal with Sample Output

Converting a binary number to an octal number can be step-by-step. For example, the binary number 110101 turns into octal as 65. This switch between base 2 and base 8's important in computing when you need compact number representation.

Let’s see what you’ll need to convert binary to octal using a C program.

What You Need Before Writing the C Program to Convert Binary to Octal

Get ready with the following:

• Knowledge of the % and / operators for remainder and division.
• Understanding of loops in C, particularly the while loop.
• Basic input/output using <stdio.h>.
• Any C compiler such as GCC 9 or newer — or just run it in the EduSeekho online compiler

Source Code of C Program to Convert Binary to Octal

Here's the source code for converting binary to octal in C. The program reads a binary number, processes groups of three bits, and outputs the corresponding octal number.

#include <stdio.h>

int main() {
    long binary, octal = 0, power = 1;
    int rem;

    // Read binary number
    printf("Enter a binary number: ");
    scanf("%ld", &binary);

    // Convert binary to octal
    while (binary != 0) {
        rem = binary % 1000;
        octal += binaryToDecimal(rem) * power;
        binary /= 1000;
        power *= 10;
    }

    printf("The octal equivalent is: %ld\n", octal);
    return 0;
}

int binaryToDecimal(int binary) {
    int decimal = 0, base = 1, lastDigit;
    while (binary) {
        lastDigit = binary % 10;
        binary /= 10;
        decimal += lastDigit * base;
        base *= 2;
    }
    return decimal;
}

Output of the Convert Binary to Octal Program

When you provide the binary number 110101, the program outputs the octal number 65. See it in action below.

Enter a binary number: 110101
The octal equivalent is: 65

Algorithm to Convert Binary to Octal in C

To convert binary to octal, the program processes the binary number in chunks of three bits and calculates their octal equivalent. Here is the step-by-step logic:

1. Initialize octal to 0 and power to 1.
2. Read the binary number from user input.
3. While the binary number isn't zero, repeat steps 4-6.
4. Extract the last three digits of the binary number.
5. Convert these three digits to their decimal equivalent.
6. Multiply this decimal by the current power of 10 and add to octal.
7. Divide the binary number by 1000.
8. Increase the power of 10.

flowchart TD
  A([Start]) --> B[/Read binary number/]
  B --> C[Initialize octal to 0]
  C --> D[Initialize power to 1]
  D --> E{"binary != 0?"}
  E -->|Yes| F["rem = binary %% 1000"]
  F --> G["decimal = rem to decimal"]
  G --> H["octal += decimal * power"]
  H --> I["binary /= 1000"]
  I --> J["power *= 10"]
  J --> E
  E -->|No| K[/Print octal/]
  K --> L([End])

How the C Program to Convert Binary to Octal Works

Let's go through how each part of the program works to convert from binary to octal.

• The program starts by including the standard I/O library with #include <stdio.h>.
• Within main(), we declare variables binary, octal, and power, initializing octal and power to 0 and 1 respectively.
• The program prompts the user to enter a binary number, reading input with scanf() into the binary variable.
• It employs a while loop to process each group of three binary digits.
• rem = binary % 1000 extracts the last three digits of the binary number.
• These three digits are then converted to decimal using the helper function binaryToDecimal().
• The octal number is updated with octal += decimal * power.
• After processing, the binary number is reduced using binary /= 1000.
• The power of 10 is increased by multiplying with 10.
• Finally, the program prints the octal equivalent using printf().

How Fast Is the C Program to Convert Binary to Octal?

Understanding how efficient the program is can help in optimizing it if needed.

Time Complexity: O(n), where n is the number of binary digits. The loop processes each group of three digits using binary /= 1000, so 9 digits need about 3 iterations.

Space Complexity: O(1) as it uses a fixed set of variables: binary, octal, power, rem, and temporary variables in the binaryToDecimal function.

Key takeaway:Chunking binary numbers in threes gets you their correct octal representation.

FAQs About C Program to Convert Binary to Octal

Here are some frequently asked questions about this program:

Related Programs

If you found this program helpful, check out these related programs:

• C Program to Convert Octal to Decimal: Full Code & Output
• C Program to Convert Decimal to Octal
• C Program to Convert Octal to Binary with Example
• C Program to Convert Binary to Decimal with Code and Output
• C Program to Convert Binary to Decimal and Vice-Versa

Conclusion

Remember to carefully process each chunk of binary digits to get the right octal number. If you’re interested in related operations, try converting binary to hexadecimal next — it’s similar. Smaller base representations make complex data easier to handle.

Test your skills further with more C programming challenges. Check out our C quiz and try this code in the C online compiler!