C. Passing pointers to be modified causing segmentation faults

I am making a decimal to binary converter in C for a class. I want to pass a char array to my function as well as the the decimal as an int. ie void DtoB(int decimal, char *array); DtoB will do the math and modify array to be the binary value. Ideally by giving it int values. Main() will just scanf(decimal), DtoB(decimal,array), and printf(array).

Here is what I have. This just returns a segmentation fault

1 #include <stdio.h>
2 #include <math.h>
3
4 void DecToBin(unsigned int, char *binary);
5
6 int main()
7 {
8         unsigned int dec;
9         char *binary[];
10         while(1) {
11                 scanf("%d", &dec);
12                 DecToBin(dec,*binary);
13                 printf("In binary is ");
14                 printf("%sn",binary);
15         }
16 }
17 void DecToBin(unsigned int dec, char *binary)
18 {
19         int counter=0;
20         while(dec) {
21                 binary[counter]=dec%2;
22                 dec/=2;
23                 counter++;
24         }
25 }

I want it done like this since this seems like the best way to be able to do 32 bit integers, while keeping the array at the minimum size. Sorry if I killed formatting. Any help is appreciated.

---

char *binary[33]

binary is array of pointers. So each element in it is a pointer.

The segmentation fault is because you are not initializing your array and trying to use it.

You are dereferencing a pointer which is not pointing to any valid memory location.

You need to allocate memory to the members of the array before using them

---

incorporating all the comments, incorporating error checking, etc. the posted code becomes :

#include <stdio.h>
#include <stdlib.h>  // exit(), EXIT_FAILURE
#include <string.h>  // memset()


// prototypes
void DecToBin(unsigned int, char *binary);

int main()
{
        unsigned int dec;
        char binary[sizeof(int)*8 +1];


        while(1)
        {
                if( 1 != scanf("%u", &dec) )
                { // then scanf failed
                    perror( "scanf for decimal value failed" );
                    exit( EXIT_FAILURE );
                }

                // implied else, scanf successful

                DecToBin(dec, binary);
                printf("In binary is ");
                printf("%sn",binary);
        }
}


void DecToBin(unsigned int dec, char *binary)
{
        size_t counter= sizeof(int)*8;

        memset( binary, ' ', counter );
        binary[ counter ] = ''; // terminate string
        counter--;

        // do...while allows for dec being 0
        do
        {
                binary[counter]= (char)((dec%2)+ 0x30);
                dec /= 2;
                counter--;
        }  while(dec);
}

which still has the shortcoming that the user is left with a blank screen and a blinking cursor. IE the code should be prompting the user, by requesting the input value.

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