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All I really know is PHP and I used the decbin function etc, It was fairly easy to do. In this C++ program I want to do the same thing, just a simple number or string how would I do this?

oni-kun
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7 Answers7

3

A simple function could be defined such as this:

void binary(int decimal) {
   int remainder;

   if(decimal <= 1) {
       std::cout << decimal;
       return;
   }
   remainder = decimal % 2;
   binary(decimal >> 1);    
   std::cout << remainder;
}

Although there are many other resources on the web on how to do this..

A noteworthy question for efficiency of it here, as you may want more than just that: Efficiently convert between Hex, Binary, and Decimal in C/C++

Community
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Nullw0rm
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    @oni-kun, C++ has a lot more to offer if you look into it, decbin isn't all that different from these solutions. – Nullw0rm May 10 '10 at 10:35
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    The parameter name `int decimal` makes no sense. Numbers aren't inherently decimal, they are just numbers. (In fact, they are always stored in binary form internally.) – fredoverflow May 10 '10 at 10:46
  • @Fred, It is decimal into binary, hence the param. He didn't specify any other data type. – Nullw0rm May 10 '10 at 10:51
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    @Null But `int` is NOT a decimal type! It just so happens that the common output routines will print an `int` as a decimal number. The calls `binary(37)` and `binary(0x25)` are completely equivalent -- the arguments are neither decimal nor hexadecimal, they are just integral numbers -- `int`s. – fredoverflow May 10 '10 at 11:24
  • @Fred the integer represents a decimal, I can make it a float or double for all it matters, the name of the `int` was decimal as that was the suggested input. – Nullw0rm May 12 '10 at 13:29
2

you can do this non-recursively using something like this:

std::string Dec2Bin(int nValue, bool bReverse = false)
{
    std::string sBin;  
    while(nValue != 0)
    {
       sBin += (nValue & 1) ? '1' : '0';
       nValue >>= 1;
    }

    if(!bReverse)        
        std::reverse(sBin.begin(),sBin.end());

    return sBin;
}

of course this isn't too architucture friendly, but it avoids cout, just incase your not using a console. it also outputs in any bit ordering.

Necrolis
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  • Maybe add replace last line with something like `return sBin.size() ? sBin : "0"`, so as to display `0` as well. – tshepang Dec 10 '12 at 14:58
1

You can use itoa if it's available on your compiler. Just remember it's not standard and if you need a standard method you're better off using the other solutions posted.

nc3b
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0

Similar to @Necrolis answer without the need for an if, and the reversal of the string.

string decimalToBinary(int decimal) {
  string binary;
  while(decimal)  {
      binary.insert(0, 1, (decimal & 1) + '0');
      decimal >>= 1;
  }
  return binary;
}
Caesar De la Paz III
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0

If you want to print it, just use this code here. If you want to return a string, instead of using cout, append to a C++ string instead.

Il-Bhima
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0

offering the iterative approach (pardon the #defines (but i'm quite sure they will be compiled to the expression's value), i don't quite remember predefined macro/constants in C):

#define INT_ARCH 32
#define ARCH_SHIFTABLE (INT_ARCH - 1)
#define ARCH_MAX_INT 1 << ARCH_SHIFTABLE

void dec_to_bin(int decimal)
{                
    int shifter = ARCH_MAX_INT;

    for(; shifter > 0; shifter >>= 1)
        cout << (decimal & shifter);        
}
Michael Buen
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0

Do with simple way in c++

#include <iostream>
using namespace std;
int main()
{
long n, rem, binary=0, i=1;
cout<<"Enter a int: ";
cin>>n;

 while(n != 0) 
   {
        rem = n%2;      
        n = n/2;        
        binary= binary + (rem*i); 
        i = i*10;
    }
cout<< "\nAns:   "<<binary <<endl;

return 0;
}
Kulamani
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