Need help with C Programming assignment

I highly suggest you review learn how to do loops. Breaking conditions are there for a reason; that reason is not to stick a random letter there.

Strings are null-terminated, so the end of the string breaks the loop.

It's a lazy way to do things, but it works so why not.
True, the nicer way to do it would be

Code:

for (i = 0; i < strlen(longstr); i++)

but it accomplishes the same thing as

Code:

for (i = 0; longstr[i][color=gray] != '\0'[/color]; i++)

anyway.