Adding 2 char arrays using binary arithmetic

This is a discussion on Adding 2 char arrays using binary arithmetic within the C++ Programming forums, part of the General Programming Boards category; Hi all, I've been writing a program to add two character arrays, which both hold a binary number and using ...

  1. #1
    Registered User
    Join Date
    Dec 2009
    Posts
    30

    Question Adding 2 char arrays using binary arithmetic

    Hi all,

    I've been writing a program to add two character arrays, which both hold a binary number and using binary arithmetic, stores the final value in another character array.

    So far, i've been pretty successful. I seem to be having trouble on the final output though. Maybe I'm having a brain fart, I dunno. But the output displays the correct binary numbers but along side various random characters.

    Preprocessor commands and function prototypes

    Code:
    #include <iostream>
    #include <math.h>
    
    void addBinaries(char[], char[], char[]);
    driver function
    Code:
    int main()
    {
    	const int MAX_ARR = 255;
    	char arrBinOne[MAX_ARR], arrBinTwo[MAX_ARR], arrFinal[MAX_ARR];
    
    	std::cout << "Please enter two binary numbers to be added..." << std::endl
    			  << "Enter 1:";
    	std::cin >> arrBinOne;
    	std::cout << "Enter 2:";
    	std::cin >> arrBinTwo;
    
    	addBinaries (arrBinOne, arrBinTwo, arrFinal);
    
            //output arrays
    	std::cout << "\n" << arrBinOne << " + " << arrBinTwo << " = " << arrFinal << std::endl;
    
    	system("PAUSE");
    	return 0;
    }

    addBinaries definition
    Code:
    void addBinaries(char binOne[], char binTwo[], char final[])
    {
    	int charToIntOne, charToIntTwo, i;
    	bool carryOver = false;
    	std::string binStore = "";
    
    	//find out how much of each array is populated
    	int arrOnePop = 0, arrTwoPop = 0;
    
    	while (binOne[arrOnePop] != '\0' || binTwo[arrTwoPop] != '\0' && arrOnePop < 255)
    	{
    		if (binOne[arrOnePop] == '1' || binOne[arrOnePop] == '0')
    			arrOnePop++;
    		
    		if (binTwo[arrTwoPop] == '1' || binTwo[arrTwoPop] == '0')
    			arrTwoPop++;
    
    		if (binOne[arrOnePop] == '\0' && binTwo[arrTwoPop] != '\0')
    		{
    			arrOnePop++;
    			binOne[arrOnePop] = '0';
    			binOne[arrOnePop + 1] = '\0';
    		}
    		if (binTwo[arrTwoPop] == '\0' && binOne[arrOnePop] != '\0')
    		{
    			arrTwoPop++;
    			binTwo[arrTwoPop] = '0';
    			binTwo[arrTwoPop + 1] = '\0';
    		}
    	}
    
    	//since both arrays are populated to be the same size, add the binary numbers right to left
    	for (i = (arrTwoPop - 1); i >= 0; i--)
    	{
    		charToIntOne = binOne[i] - '0';
    		charToIntTwo = binTwo[i] - '0';
    
    		if (carryOver == true && (charToIntOne + charToIntTwo) >= 1)
    		{
    			binStore += "0";
    		}
    		else if (carryOver == true && (charToIntOne + charToIntTwo) == 0)
    		{
    			binStore += "1";
    			carryOver = false;
    		}
    		else
    		{
    			if ((charToIntOne + charToIntTwo) > 1)
    			{
    				binStore += "0";
    				carryOver = true;
    			}
    			else if ((charToIntOne + charToIntTwo) == 1)
    			{
    				binStore += "1";
    				carryOver = false;
    			}
    			else
    			{
    				binStore += "0";
    				carryOver = false;
    			}
    		}
    	}
           //in the event that there was one last carry over, add it to string
    	if (carryOver == true)
    	{
    		binStore += "1";
    	}
    	
    	//convert binary storage string to a char array
    	for (int j = 0; j < binStore.size(); j++)
    	{
    		final[binStore.size() - j] = binStore.at(j);
    	}
            return;
    }

    I'm pretty sure it will be in the addBinaries() function, but i'm not too sure. Maybe it's something I'm missing when adding the binary arrays.

    Thank you for any help you can give, and if you have any questions, please ask.

  2. #2
    Registered User
    Join Date
    Dec 2009
    Posts
    30
    Almost fixed it. I figured that since I'm trying to use C-Strings, that adding the termination character '\0' at the end of final[] would help (and it did!). Now I have a couple of strange characters in front of the final array.


    added code in addBinaries
    Code:
    //convert binary storage string to a char array
    	for (int j = 0; j < binStore.size(); j++)
    	{
    		final[binStore.size() - j] = binStore.at(j);
    	}
    	final[binStore.size() + 1] = '\0';
    	return;
    }

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