Binary Multiplication

[EdwardVX]

I'm trying to make a binary calculator and I just can't find what's going wrong:

#include <stdio.h>
void dec2bin(long decimal, char *binary);
void dec2bin1(long decimal2, char *binary2);

int binaryAddition(int,int);

int main(void){

    long int binarym1,binarym2,multiply=0;
    int digit,factor=1;
      long decimal;
  long decimal2;
    char binary[80];
  char binary2[80];


  printf("\n\n Please enter the first value : ");
  scanf("%ld",&decimal);
  dec2bin(decimal,binary);
  printf("\n\n Now enter a second value : ");
  scanf("%ld",&decimal2);
  dec2bin1(decimal2,binary2);
  printf("\n The binary value of %ld is %s \n",decimal,binary);
  printf("\n The binary value of %ld is %s \n",decimal2,binary2);
  
  binarym1 =  (long int) binary;
  binarym2 = (long int) binary2;
  
   printf("\n The binary is %s \n",binarym1); //test - please ignore

    while(binarym2!=0){
         digit =  binarym2 %10;

         if(digit ==1){
                 binarym1=binarym1*factor;
                 multiply = binaryAddition(binarym1,multiply);
         }
         else
             binarym1=binarym1*factor;
   
         binarym2 = binarym2/10;
         factor = 10;
    }
    printf("The answer is: %ld",multiply);
  getchar();  // wait   
  getchar();  // wait
  return 0;
}



int binaryAddition(int binarym1,int binarym2){

    int i=0,remainder = 0,sum[20];
    int binarySum=0;

    while(binarym1!=0||binarym2!=0){
         sum[i++] =  (binarym1 %10 + binarym2 %10 + remainder ) % 2;
         remainder = (binarym1 %10 + binarym2 %10 + remainder ) / 2;
         binarym1 = binarym1/10;
         binarym2 = binarym2/10;
    }

    if(remainder!=0)
         sum[i++] = remainder;
    --i;
    while(i>=0)
         binarySum = binarySum*10 + sum[i--];

    return binarySum;
}
void dec2bin(long decimal, char *binary)
{
  int  k = 0, n = 0;
  int  neg_flag = 0;
  char temp[80];
  int  remain;

  // take care of negative input
  if (decimal < 0)
  {      
    decimal = -decimal;
    neg_flag = 1;
  }
  do 
  {
    remain    = decimal % 2;
    // whittle down the decimal number
    decimal   = decimal / 2;
    // converts digit 0 or 1 to character '0' or '1'
    temp[k++] = remain + '0';
  } while (decimal > 0);

  if (neg_flag)
    temp[k++] = '-';       // add - sign
  else
    temp[k++] = ' ';       // space

  while (k >= 0)
    binary[n++] = temp[--k];

  binary[n-1] = 0;         
}

void dec2bin1(long decimal2, char *binary2)
{
  int  k = 0, n = 0;
  int  neg_flag = 0;
  char temp[80];
  int remain1;

  // take care of negative input
  if (decimal2 < 0)
  {      
    decimal2 = -decimal2;
    neg_flag = 1;
  }
  do 
  {
    remain1    = decimal2 % 2;
    decimal2   = decimal2 / 2;
    // converts digit 0 or 1 to character '0' or '1'
    temp[k++] = remain1 + '0';
  } while (decimal2 > 0);

  if (neg_flag)
    temp[k++] = '-';       // add - sign
  else
    temp[k++] = ' ';       // space

  while (k >= 0)
    binary2[n++] = temp[--k];

  binary2[n-1] = 0;        
}

Output Example:

Please enter the first value: 45
Now enter a second value: 22
The binary value of 45 is  101101
The binary value of 22 is  10110
The answer is: 0

Funny thing is it produces NO error messages so I have no clue what's going on... help...

[EdwardVX]

Hello, anyone?

[shibblez]

In lines 26 and 27 you're casting a string to a long. What you probably mean to do is convert the string to a long. I think you'll find that atol() is what you need.

The reason that there a no error is that it's doing what you asked for and not what you wanted.

[shibblez]

What development environment are you using?

[EdwardVX]

I'm using Dev C++ to develop this program. Although this is a C Program (it must be a C, not C++.)

Still not working unless I'm missing something.

[EdwardVX]

----Sorry ignore this, though I solved it. ----

[EdwardVX]

*thought

Made a serious typo there. Okay it half half works now. However anything over 8 bits and it messes up. For example: 3579 x 42 would give me an incorrect answer.

[shibblez]

Post the current code and a sample of the output and we'll see what we can do

[EdwardVX]

#include <stdio.h>
#include <stdlib.h>

void dec2bin(long decimal, char *binary);
void dec2bin1(long decimal2, char *binary2);

int binaryAddition(long long,long long);

int main(void){

    long int binarym1,binarym2, multiply=0;
    int digit,factor=1;
  long decimal;
  long decimal2;
  char binary[80];
  char binary2[80];


  printf("\n\n Please enter the first value : ");
  scanf("%ld",&decimal);
  dec2bin(decimal,binary);
  printf("\n\n Now enter a second value : ");
  scanf("%ld",&decimal2);
  dec2bin1(decimal2,binary2); 
  binarym1 = atoll(binary);
  binarym2 = atoll(binary2);
     printf("\n  %ld\n",binarym1);
   printf(" x %ld \n",binarym2); 
      printf("   =======\n");

    while(binarym2!=0){
         digit =  binarym2 %10;

         if(digit ==1){
                 binarym1=binarym1*factor;
                 multiply = binaryAddition(binarym1,multiply);
         }
         else
             binarym1=binarym1*factor;
   
         binarym2 = binarym2/10;
         factor = 10;
    }
    printf("%ld \n",multiply);
          printf("   =======");
  getchar();  // wait   
  getchar();  // wait
  return 0;
}



int binaryAddition(long long binarym1, long long binarym2){

    int i=0,remainder = 0,sum[20];
    int binarySum=0;

    while(binarym1!=0||binarym2!=0){
         sum[i++] =  (binarym1 %10 + binarym2 %10 + remainder ) % 2;
         remainder = (binarym1 %10 + binarym2 %10 + remainder ) / 2;
         binarym1 = binarym1/10;
         binarym2 = binarym2/10;
    }

    if(remainder!=0)
         sum[i++] = remainder;
    --i;
    while(i>=0)
         binarySum = binarySum*10 + sum[i--];

    return binarySum;
}
void dec2bin(long decimal, char *binary)
{
  int  k = 0, n = 0;
  int  neg_flag = 0;
  char temp[80];
  int  remain;

  // take care of negative input
  if (decimal < 0)
  {      
    decimal = -decimal;
    neg_flag = 1;
  }
  do 
  {
    remain    = decimal % 2;
    // whittle down the decimal number
    decimal   = decimal / 2;
    // converts digit 0 or 1 to character '0' or '1'
    temp[k++] = remain + '0';
  } while (decimal > 0);

  if (neg_flag)
    temp[k++] = '-';       // add - sign
  else
    temp[k++] = ' ';       // space

  while (k >= 0)
    binary[n++] = temp[--k];

  binary[n-1] = 0;         
}

void dec2bin1(long decimal2, char *binary2)
{
  int  k = 0, n = 0;
  int  neg_flag = 0;
  char temp[80];
  int remain1;

  // take care of negative input
  if (decimal2 < 0)
  {      
    decimal2 = -decimal2;
    neg_flag = 1;
  }
  do 
  {
    remain1    = decimal2 % 2;
    decimal2   = decimal2 / 2;
    // converts digit 0 or 1 to character '0' or '1'
    temp[k++] = remain1 + '0';
  } while (decimal2 > 0);

  if (neg_flag)
    temp[k++] = '-';       // add - sign
  else
    temp[k++] = ' ';       // space

  while (k >= 0)
    binary2[n++] = temp[--k];

  binary2[n-1] = 0;        
}

Output:

Please enter the first value : 3579
Now enter a second value : 42
-1558038685
x 101010
======
1483726590
======

[shibblez]

I see what the problem is. The conversion to binary is working fine, however
3579 is 110111111011b
Maximum long int is 2147483647 assuming a 32 bit word, so the largest number that this will handle is 1111111111b = 1023

[EdwardVX]

Yeah I kinda knew that, I tried changing to "long long" on these variables but it doesn't seem to be working either.

[shibblez]

What does it do?