1. A character string correction system for use in an information processing system for analyzing a morpheme by comparing an input character string with a dictionary entry, comprising: dictionary storage means for storing a dictionary having entries of input characters to be compared with characters in the input character string; error pattern storage means for storing an error pattern prescribing a type of possible error in the input character string and for storing the error pattern comprising a fault pattern representing a character pattern of a possible error and a correct pattern representing a correct character pattern corresponding to the fault pattern; and retrieval means for searching the dictionary stored in said dictionary storage means using the error pattern stored in said error pattern storage means retrieving the dictionary entry corresponding to the input character string, outputting the retrieved dictionary entry as a candidate for a recognized word, generating an alternative character replacing a first character by referring to the correct pattern when the first character corresponding to the fault pattern is input, and searching the dictionary using the alternative character.