Decimal to Binary Conversion program

Hello, I wrote this program for my Intro to Digital Systems class to convert a base 10 number into a Binary base 2 number string. It works perfectly except for some numbers it slams a number in front of it. On linux this number is -1073742772. Such a number is 60.

Code:

---

#include <stdio.h>


int main()
{
        int input=0;
        int count=0;
        int binary_backwards[32];
        int binary_string[32];
        int i=0;
        int j=0;
        printf("Enter a base 10 positive number to convert to binary:");
        scanf("%i", &input);

        while(input >0 && count<32)
        {       
                binary_backwards[count] = input %2;
                input /=2;
                count++;
        }

        while(count >-1)
        {
                binary_string[i]=binary_backwards[count];
                count--;
                i++;
        }
       
        while(j<i)
        {
                printf("%i", binary_string[j]);
                j++;
        }
        return 0;
}

---

Anyone have any ideas why this is happening?

You incremented count after inserting your last binary digit into binary_backwards.

You should also consider not using fixed numbers (32), and instead consider using provided limits instead:

Code:

---

#include<limits.h>
...
for( x = 0; x < sizeof( int ) * CHAR_BIT; x++ )
    ...

---

This will ensure that it works correctly for say, old crappy DOS compilers that most people around here seem to use. ;)


Quzah.

here is what i would do to fix it

replace the code below which is in your program

Code:

---

while(count >-1) {
    binary_string[i]=binary_backwards[count];
    count--;
    i++;
}

while(j<i) {
    printf("%i", binary_string[j]);
    j++;
}

---

with this

Code:

---

while ((--count) > -1)
    printf("%d", binary_backwards[count]) ;

---

hence you can also get rid of

Code:

---

int binary_string[32];
int i=0;
int j=0;

---

i'm new to c aswell hope i've been a help.

You can do this in more simpler!

A different tack:

Code:

---

#include <stdio.h>

void dectobin(int value)
{
  if ( value )
  {
      dectobin(value / 2);
      printf("%d", value % 2);
  }
}

int main(void)
{
  dectobin(12345);
  putchar('\n');
  dectobin(60);
  putchar('\n');
  return 0;
}

/* my output
11000000111001
111100
*/

---