I used Word Writer 4 on the C64.  Its spell-check system avoided loading the entire dictionary into memory or using an on-disk structured random-access database.  Instead, it simply sorted the words in your document first, then stepped through this list while sequentially reading the sorted dictionary from disk.  You could watch this process on the screen while it was happening.<p>Needless to say, spell checking was a lengthy task that you invoked sparingly. :)