Thread: Converting Decimal to Binary

Hello all,

This is my project..
"Write a function to return the binary representation of the number x as a character string. For example : if x = 17 is passed to the function the return value should be a pointer to the string
00000000000000000000000000010001.
Below please find the main function to test your code."

So I have written the code and have gotten it to work but I cannot figure out how to get it to work so that "the return value should be a pointer to the string." as of now I have in commented out because it is printing out the binary number twice. But if I comment out the for loop and printf statement in the function and run it I dont get anything. Im still very new to C so any help would be appreciated. Thanks!

Code:

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

char *int_to_binary(int);
char b[80];
int main(void)
{                                           // Call function int_to_binary to print a number in binary
    int x=0;
    char *ptr;

    if(setvbuf(stdout, NULL, _IONBF,0))
    {
        perror("failed to change the buffer of stdout");
        return EXIT_FAILURE; //clears buffer
    }

    printf("This program will convert the users input from decimal to binary.\n");
    printf("Enter a decimal number: ");
    scanf("%d",&x);
    ptr = int_to_binary(x);
    //printf("%s\n", int_to_binary(x));
    return 0;
}

char *int_to_binary(int x)
{
    int i;
    for(i=31; i>=0; i--)
    {
        b[i]= x%2;
        x/=2;
    }
    b[33]='\0';
    for(i=0; i<=31;i++)
        printf("%d",b[i]); 
    return b;
}