Editing Spell checker (section)

== Functionality ==
The first spell checkers were "verifiers" instead of "correctors." They offered no suggestions for incorrectly spelled words. This was helpful for [[typos]] but it was not so helpful for logical or phonetic errors. The challenge the developers faced was the difficulty in offering useful suggestions for misspelled words. This requires reducing words to a skeletal form and applying pattern-matching algorithms.

It might seem logical that where spell-checking dictionaries are concerned, "the bigger, the better," so that correct words are not marked as incorrect. In practice, however, an optimal size for English appears to be around 90,000 entries. If there are more than this, incorrectly spelled words may be skipped because they are mistaken for others. For example, a linguist might determine on the basis of [[corpus linguistics]] that the word ''[[baht]]'' is more frequently a misspelling of ''bath'' or ''bat'' than a reference to the Thai currency. Hence, it would typically be more useful if a few people who write about Thai currency were slightly inconvenienced than if the spelling errors of the many more people who discuss baths were overlooked.
[[Image:English-language screenshot of Enchant, AbiWord's spell checker - The quick brown fox jumps over the lazy dog.png|right|thumb|A screenshot of [[Enchant (software)|Enchant]], the [[AbiWord]] spell checker]]
The first MS-DOS spell checkers were mostly used in proofing mode from within word processing packages. After preparing a document, a user scanned the text looking for misspellings. Later, however, batch processing was offered in such packages as [[Oracle Corporation|Oracle]]'s short-lived CoAuthor and allowed a user to view the results after a document was processed and correct only the words that were known to be wrong. When memory and processing power became abundant, spell checking was performed in the background in an interactive way, such as has been the case with the Sector Software produced Spellbound program released in 1987 and [[Microsoft Word]] since Word 95.

Spell checkers became increasingly sophisticated; now capable of recognizing [[grammatical]] errors. However, even at their best, they rarely catch all the errors in a text (such as [[homophone]] errors) and will flag [[neologism]]s and foreign words as misspellings. Nonetheless, spell checkers can be considered as a type of [[foreign language writing aid]] that non-native language learners can rely on to detect and correct their misspellings in the target language.<ref>Banks, T. (2008). [http://eric.ed.gov/PDFS/ED501062.pdf ''Foreign Language Learning Difficulties and Teaching Strategies'']. (pp. 29). Master's Thesis, Dominican University of California. Retrieved 19 March 2012.</ref>