Aspect that need consideration:

• encoding of strings (MBCS / UTF8)
• Traits / locale for comparison (string collation) Do diacritics matter? Also see: https://learn.microsoft.com/en-us/windows/win32/intl/sort-order-identifiers

Now, if it's just UK post codes (NW3 6SG), then well, |0x20 for A-Z and byte compare. But does the space matter? You might have some special rules.

And for prefix searches, one has to check the function used (e.g. stricmp) for what happens when one string is shorter than the other.

The sad reality is that there are MANY string comparisons that can be used, but the edge cases are complex.

TL;DR: just roll your own, depending on your needs.