C++ program to convert binary to octal

Here is a C++ program to convert binary to octal. Here are the different methods to convert binary to octal like using recursion.
How to convert binary to octal (base 2 to base 8).
To convert binary to octal just take three bits and convert it in decimal number .For example let us convert binary number (101011)₂ to octal.
(011)₂ decimal equivalent is 3
(101)₂ decimal equivalent is 5
Thus octal equivalent of binary number (101011)₂ is (53)₈.

Method 1 : C++ program to convert binary to octal

#include<iostream>
#include<math.h>
using namespace std;
int main()
{
    long octal=0,rem,num,temp=1,z=0;
    cout<<"Enter the number in binary ";
    cin>>num;
    while(num>0)
    {
        for(int y=0;y<3;y++)
        {
             rem=num%10;
             num/=10;
             octal+=rem*pow(2,y);
       }
       z+=octal*temp;
       octal=0;
       temp*=10;
    }
    cout<<"Octal equivalent "<<z;
    return 0;
}

Method 2 : C++ program to convert binary to octal using recursion

#include<iostream>
#include<math.h>
using namespace std;
int deci(int n,int i)
{
    if(n==0)
        return 0;
    return (n%10)*pow(2,i)+deci(n/10,i+1);
}
void octal(int n)
{
    if(n==0)
        return;
    octal(n/1000);
    cout<<deci(n%1000,0);
}
int main()
{
    int num;
    cout<<"Enter Binary number : ";
    cin>>num;
    cout<<"Octal equivalent : ";
    octal(num);
    return 0;
}

Method 3 : C++ program to convert binary to octal using function

#include<iostream>
#include<math.h>
#include<string.h>
using namespace std;
void octal(int num)
{
    int octal=0,rem,temp=1,z=0;
    while(num>0)
    {
        for(int y=0;y<3;y++)
        {
             rem=num%10;
             num/=10;
             octal+=rem*pow(2,y);
       }
       z+=octal*temp;
       octal=0;
       temp*=10;
    }
    cout<<"Octal equivalent "<<z;
}
int main()
{
    int num;
    cout<<"Enter the number in binary ";
    cin>>num;
    octal(num);
    return 0;
}

Method 4 : C++ program to convert binary to octal and store it as string

#include<iostream>
#include<math.h>
#include<string.h>
using namespace std;
int main()
{
    char bin[30],octal[10];
    int i=0,z=0,y=0,temp=0;
    cout<<"Enter the number in binary ";
    cin>>bin;
    z=strlen(bin)-1;
    while(z>=0)
    {
        for(y=0;y<3&&z>=0;y++)
             temp+=(bin[z--]-48)*pow(2,y);
        octal[i++]=temp+48;
        temp=0;
    }
    octal[i]='\0';
    strrev(octal);
    cout<<"Octal equivalent "<<octal;
    return 0;
}