Octal to Decimal Conversion in C++

Given with an octal number as an input, the task is to convert the given octal number into a decimal number.

Decimal numbers in computer is represented with base 10 and octal number is represented with base 8 starting from the digit 0 till 7 whereas decimal numbers can be any numeric digit starting from 0 – 9.

To convert an octal number into a decimal number follow these steps −

• We will extract digits starting from right to left through a remainder and then multiply it with the power starting from 0 and will be increased by 1 till the (number of digits) – 1
• Since we need to do conversions from octal to binary the base of power will be 8 as octal have base 8.
• Multiply the digits of given inputs with base and power and store the results
• Add all the multiplied values to obtain the final result which will be a decimal number.

Given below is the pictorial representation of converting an octal number into a decimal number.

Example

Input-: 451
   1 will be converted to a decimal number by -: 1 X 8^0 = 1
   5 will be converted to a decimal number by -: 5 X 8^1 = 40
   4 will be converted to a decimal number by -: 4 X 8^2 = 256
Output-: total = 0 + 40 + 256 = 10

Algorithm

Start
Step 1-> declare function to convert octal to decimal
   int convert(int num)
      set int temp = num
      set int val = 0
      set int base = 1
      Set int count = temp
      Loop While (count)
         Set int digit = count % 10
         Set count = count / 10
         Set val += digit * base
         Set base = base * 8
      End
      return val
step 2-> In main()
   set int num = 45
   Call convert(num)
Stop

Example

 Live Demo

#include <iostream>
using namespace std;
//convert octal to decimal
int convert(int num) {
   int temp = num;
   int val = 0;
   int base = 1;
   int count = temp;
   while (count) {
      int digit = count % 10;
      count = count / 10;
      val += digit * base;
      base = base * 8;
   }
   return val;
}
int main() {
   int num = 45;
   cout <<"after conversion value is "<<convert(num);
}

Output

IF WE RUN THE ABOVE CODE IT WILL GENERATE FOLLOWING OUTPUT

after conversion value is 37