programming-for-dummies

Searching Phonetically 433
If you had the strings Harry stored in a text file, the Soundex algorithm converts
that string into the H600 code. Now if you searched for the string hairy
with the Soundex algorithm, the computer converts hairy into the Soundex
code H600 and then finds the same H600 code stored at the string Harry,
thus finding a matching string phonetically.
Phonetic algorithms are used most often in spell checkers. The algorithm
calculates a code for each misspelled word and then matches that code to
correctly spelled words that have the same phonetic code.
String searching algorithms must examine every character, so the only way to
speed up an algorithm is to simplify how it examines a string of text. Paradoxically,
string searching algorithms often run faster by organizing text in a specific
way and then searching that method of organization rather than the actual
text itself, which is how the Shift Or and Soundex algorithms work. As a general
rule, the faster the string searching algorithm, the harder and more complicated
it is to implement.
Book IV
Chapter 3
String Searching