Compiler warning when dealing with strings

[stratovarius519]

Hey guys,
I am supposed to find a substring in a string of characters.Here is my code:
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
int find(char *a, char *key);
int main(void)
{
char string[30];
char substr[10];
char exist;

printf("Enter the string: ");
gets(string);
printf("Enter the substring: ");
gets(substr);

exist = find(string,substr);
if (exist != NULL)
printf("Found that part in original string\n");
else
printf("Have not found that part in original string\n");

return 0;
}
int find(char *a, char *key)
{
while(*a != '\0'){
if(*a == *key)
return (1);
else
return (0);
}
}

Now, it seems to work fine but I get this warning from Borland C++: Function should return a value in function find.

I thought it did return a value which is either a pointer to a substring or a NULL pointer.Ideas?

[Salem]

> Function should return a value in function find.
If your while loop executes zero times, then the function just falls off the end with no return statement, since both return statements are inside the while loop

It also only compares the first char - there is no a++ or key++ to compare successive chars

> I thought it did return a value which is either a pointer to a substring or a NULL pointer.Ideas?
Looks like 0 or 1 to me

If you want to return a pointer, then the function should return a char *