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?

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--)

         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++)

  • \$\begingroup\$ For size, use constexpr, rather than const. \$\endgroup\$
    – JNS
    Apr 8, 2015 at 16:29

2 Answers 2

  • 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)

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);

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