Digital to Binary

I'm trying to figure out how to add the 0's in front of the binary out put.

ie: when I enter 23 I get 10111 I would like it to read 00010111 or 0001 0111

Thanks for any help you can give me on this.

Code:

#include <stdio.h>
#include <conio.h>

int main(void)
{
    long b[20], n, r, c = 0, i ;
    printf("Enter a decimal number: ");
    scanf("%ld", &n) ;

    if(n <= 0 || n > 255)
    {
        printf("Only numbers between 1 - 255");
        return 1;
    }
    while(n > 0)
    {
        r = n % 2 ;
        b[c] = r ;
        n = n / 2 ;
        c++ ;
    }
    printf("The binary equivalent is : ");

    for(i = c - 1 ; i >= 0; i--)
    {
        printf("%ld", b[i]) ;
    }
}

Why not set all the values originally to 0 then make sure the for loop that does the print statement is setup in a different manner so it goes through 8 iterations

You need to replace your while loop with a for loop, the number of iterations matching the number of digits you want.

It is better to write a helper function to do the conversion. For example:

Code:

/* Convert value to binary.
 * buffer must have room for at least (digits + 1) chars.
*/
char *to_binary(char *const buffer, int digits, unsigned long value)
{
    buffer[digits] = '\0';

    while (digits-- > 0) {
        buffer[digits] = '0' + (left & 1UL);
        left /= 2UL;
    }

    return buffer;
}

To use this, you can do for example

Code:

int main(void)
{
    char  string[10];
    int   number;

    number = 85;

    printf("%d in decimal is %s in binary.\n", number, to_binary(string, 8, number));

    return 0;
}

Thanks

Originally Posted by Sorinx

Why not set all the values originally to 0 then make sure the for loop that does the print statement is setup in a different manner so it goes through 8 iterations

Thanks so much- This gives me something to go with.

With your example would I declare left as

int left; or left = 0;

It's undeclared

Thanks
Bob

Originally Posted by Nominal Animal

You need to replace your while loop with a for loop, the number of iterations matching the number of digits you want.

It is better to write a helper function to do the conversion. For example:

Code:

/* Convert value to binary.
 * buffer must have room for at least (digits + 1) chars.
*/
char *to_binary(char *const buffer, int digits, unsigned long value)
{
    buffer[digits] = '\0';

    while (digits-- > 0) {
        buffer[digits] = '0' + (left & 1UL);
        left /= 2UL;
    }

    return buffer;
}

To use this, you can do for example

Code:

int main(void)
{
    char  string[10];
    int   number;

    number = 85;

    printf("%d in decimal is %s in binary.\n", number, to_binary(string, 8, number));

    return 0;
}

Ouch. Copy-paste error. Replace left with value.

Code:

/* Convert value to binary.
 * buffer must have room for at least (digits + 1) chars.
*/
char *to_binary(char *const buffer, int digits, unsigned long value)
{
    buffer[digits] = '\0';

    while (digits-- > 0) {
        buffer[digits] = '0' + (value & 1UL);
        value /= 2UL;
    }

    return buffer;
}

Ok thanks....

Originally Posted by Nominal Animal

Ouch. Copy-paste error. Replace left with value.

Code:

/* Convert value to binary.
 * buffer must have room for at least (digits + 1) chars.
*/
char *to_binary(char *const buffer, int digits, unsigned long value)
{
    buffer[digits] = '\0';

    while (digits-- > 0) {
        buffer[digits] = '0' + (value & 1UL);
        value /= 2UL;
    }

    return buffer;
}