I remember when I was about twelve or thirteen, seeing some mention of automatic spelling checking, trying to figure out how it could be done, and ending up very skeptical. It seemed to me there just wasn't enough regularity for any compact algorithm to do the job, so it just couldn't be done without literally having a list of every word in the English language, and even if you had a 64K machine, that wouldn't fit in memory alongside a word processor and your document.