int find_ substr( char *s1, char *s2)
{
register int t;
char *p, *p2;
for( t= 0; s1[ t]; t++) {
p = &s1[ t];
p2 = s2;
while(* p2 && *p2==* p) {
p++;
p2++;
}
if(!* p2) return t; /* substring was found */
}
return -1; /* substring not found */
}

for( t= 0; s1[ t]; t++)

int find_ substr( char *s1, char *s2)
{
    register int t;
    char *p, *p2;
    for( t= 0; s1[t]; t++)  // Move character by character thru the source string
                            // start at the first character t=0 and s1[t] 
                            // until the current character s1[t] is 0 (FALSE)
    {
        p = &s1[t];         // p becomes the address of the current character
        p2 = s2;            // p2 becomes the search string
 
// Following tests to see if the current position in the source string and the seach string
// matches...
        while (*p2  &&      // Continue while *p2 is not 0 (TRUE) -- end of string not found
               *p2 == *p)   //            and source and search characters are identical
        {
            p++;            // skip to the next character
            p2++;           //    in both strings
        }
        if (!*p2) return t; // out of loop -- if the current character in the seach string
                            //    is 0, we have a match.  Return the substript of the start
                            //    of the sub-string
    }
    return -1;  // substring not found 
}

#include <iostream>
using namespace std;
 
int main()
{
    cout << "Hello, World!";
}