Algorithm

Octal to Decimal Conversion Algorithm:

1. Input:

• Accept an octal number as input.
2. Initialize Variables:

• Initialize a variable `decimal` to 0.
• Initialize a variable `base` to 1.
3. Convert:

• Starting from the rightmost digit, multiply each digit of the octal number by the corresponding power of 8 and add it to the `decimal` variable.
• Update the `base` by multiplying it by 8 for each digit.
4. Output:

• The final value of `decimal` is the equivalent decimal representation of the given octal number.

Decimal to Octal Conversion Algorithm:

1. Input:

• Accept a decimal number as input.
2. Initialize Variables:

• Initialize an array to store the octal digits.
• Initialize a variable `index` to 0.
3. Convert:

• Divide the decimal number by 8, store the remainder as the current octal digit, and update the decimal number with the quotient.
• Repeat the above step until the decimal number becomes 0.
• Store each octal digit in the array.
4. Output:

• The octal representation is obtained by reading the array in reverse order.

Code Examples

#1 Code Example- C Programing to Convert Decimal to Octal

```Code - C Programming```

``````#include <stdio.h>
#include <math.h>

// function prototype
int convertDecimalToOctal(int decimalNumber);

int main() {

int decimalNumber;

printf("Enter a decimal number: ");
scanf("%d", &decimalNumber);

printf("%d in decimal = %d in octal", decimalNumber, convertDecimalToOctal(decimalNumber));

return 0;
}

// function to convert decimalNumber to octal
int convertDecimalToOctal(int decimalNumber) {
int octalNumber = 0, i = 1;

while (decimalNumber != 0) {
octalNumber += (decimalNumber % 8) * i;
decimalNumber /= 8;
i *= 10;
}

return octalNumber;
}
``````
Copy The Code &

Output

cmd
Enter a decimal number: 78
78 in decimal = 116 in octal

#2 Code Example-C Programing to Convert Octal to Decimal

```Code - C Programming```

``````#include <stdio.h>
#include <math.h>

// function prototype
long long convertOctalToDecimal(int octalNumber);

int main() {

int octalNumber;

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

printf("%d in octal = %lld in decimal", octalNumber, convertOctalToDecimal(octalNumber));

return 0;
}

// function to convert octalNumber to decimal
long long convertOctalToDecimal(int octalNumber) {
int decimalNumber = 0, i = 0;

while(octalNumber != 0) {
decimalNumber += (octalNumber%10) * pow(8,i);
++i;
octalNumber/=10;
}

i = 1;

return decimalNumber;
}

``````
Copy The Code &

Output

cmd
Enter an octal number: 116
116 in octal = 78 in decimal

#3 Code Example- C Programing Check for Octal Number and Convert it to Decimal

```Code - C Programming```

``````#include <stdio.h>
#include <math.h>

// function prototypes
int checkOctal(int);
long long convertOctalToDecimal(int);

int main() {

int octalNumber;
int condition;

// repeat loop as long as user
// gives a non-octal number
do {
printf("Enter an octal number: ");
scanf("%d", &octalNumber);

// check if number is octal
condition = checkOctal(octalNumber);

if (!condition) {
printf("%d is not an octal number!\n", octalNumber);
}
} while (condition == 0);

printf("%d in octal = %lld in decimal", octalNumber, convertOctalToDecimal(octalNumber));

return 0;
}

// function to check octal number
int checkOctal(int octalNumber) {
int remainder;

// check each digit of input number
while(octalNumber != 0) {
remainder = octalNumber % 10;

// return 0 if a digit is 8 or 9
if (remainder >= 8) {
return 0;
}

octalNumber/= 10;
}

// return 1 if number is octal
return 1;
}

// function to convert octalNumber to decimal
long long convertOctalToDecimal(int octalNumber) {
int decimalNumber = 0, i = 0;

while(octalNumber != 0) {
decimalNumber += (octalNumber%10) * pow(8,i);
++i;
octalNumber/=10;
}

i = 1;

return decimalNumber;
}
``````
Copy The Code &

Output

cmd
Enter an octal number: 96
96 is not an octal number!
Enter an octal number: 25
25 in octal = 21 in decimal