Doug McIlroy's mot, "If the only tool you have is a hammer, everything looks like a nail . . .", is apposite here. Bit maps and one-bit counts have many limitations, as do pools, stacks, queues, trees, usw.
But, as Bill Fairchild has just made abundantly clear, spelling checkers are unsatisfactory not because they use or omit to use bit maps but because they are not context-sensitive. Homonyms abound in English because of its mongrel vocabulary. Subliterate English speakers confuse them or, better, do not know that they need to be distinguished; and now, courtesy of the internet, these subliterate speakers of English are subliterate writers of English too. All this was predictable, and it was indeed predicted long ago by Ortega y Gasset. John Gilmore Ashland, MA 01721-1817 USA .
