Simple Binary Adder

Question

The program adds two binary numbers in two' s complement ignoring the overflow for a constant size of bits. I am trying to generalize the program by taking input from the user in a single line without memory wastage. Is there any way to achieve this?

#include<iostream.h>
#include<conio.h>
void main ()
{
 const int size=9;
 enum bool {a=0, b=1};
 bool carry,dummy;
 bool array[size]={0,0,1,1,1,1,1,0,1};
 bool reg[size]= {1,0,1,1,1,0,1,0,1};
 for (int i=(size-1); i>=0 ; i--)
 {
 dummy=reg[i];
 reg[i]= (!reg[i]) && (array[i] !=carry) || reg[i] && (array[i]==carry);
 carry=(array[i]&&dummy) || (dummy&&carry) || (array[i]&&carry);
 }
 for (int j=0 ; j<size ; j++)
 {
 cout<<reg[j];
 }
}

• JNS: For size, use constexpr, rather than const.

Answer 1

• Everything is in main. You need to make binary_add function, which only adds things. It may even return interesting things (aka condition flags).

• carry is not initialized.

• I don't see how do you use enum bool.

• I don't see why do you #include <conio.h>

• Be consistent with spaces. carry computation is very crowded. Make it

  (array[i] && dummy) || (dummy && carry) || (array[i] && carry)
  

Answer 2

Rather than converting to what is basically an integer array, which uses 16 bits per element, you'll find it much easier and more memory efficient to use a bitset<>, which stores 1 bit per element. With this you can cheat and convert the decimal addition to a bitset:

const size_t BIT_LENGTH = 9;
bitset<BIT_LENGTH> AddBinary(int numA, int numB)
{
 bitset<BIT_LENGTH> answer(numA + numB);
 return answer;
}

Or if you truly want bit manipulation something like this would work:

bitset<BIT_LENGTH> AddBinary(int numA, int numB)
{
 bitset<BIT_LENGTH> binaryA(numA);
 bitset<BIT_LENGTH> binaryB(numB);
 bitset<1> carry;
 for (int i = 0; i < BIT_LENGTH; i++)
 {
 bitset<2> temp(binaryA[i] + binaryB[i] + carry[0]);
 binaryA[i] = temp[0];
 carry[0] = temp[1];
 }
 return binaryA;
}

Now you can get the user to input integers and displaying the results is a simple matter of:

cout << AddBinary(numa,numb);