Decimal to Binary Conversion in a String

/*
Write a program in C for decimal to binary conversion in string
*/

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

char *decimal_to_binary(int);

main()
{
int n, c, k;
char *pointer;

printf("Enter an integer in decimal number system\n");
scanf("%d",&n);

pointer = decimal_to_binary(n);
printf("Binary string of %d is: %s\n", n, t);

free(pointer);

return 0;
}

char *decimal_to_binary(int n)
{
int c, d, count;
char *pointer;

count = 0;
pointer = (char*)malloc(32+1);

if ( pointer == NULL )
exit(EXIT_FAILURE);

for ( c = 31 ; c >= 0 ; c-- )
{
d = n >> c;

if ( d & 1 )
*(pointer+count) = 1 + '0';
else
*(pointer+count) = 0 + '0';

count++;
}
*(pointer+count) = '\0';

return pointer;
}