16. A computer program product, tangibly stored on a machine-readable medium, comprising instructions operable to cause a programmable processor to perform operations comprising: receiving an input character string comprising a plurality of characters in the Roman alphabet, the input character string including a leading character; comparing the leading character to words included in a dictionary including records registering words formed from the Roman alphabet; iteratively comparing the leading character plus adjacent characters in the input character string to words included in the dictionary at least n times, wherein n is a positive integer, until the following conditions are satisfied: the leading character plus (n−1) adjacent characters matches a word in the dictionary, the leading character plus n adjacent characters does not match a word in the dictionary, and the leading character plus n+1 or more adjacent characters cannot match a word in the dictionary wherein the dictionary includes records registering the words, each record including a registered word field, a converted word field and a field indicating whether or not the registered word has an included word, and for records where the registered word has an included word, a plurality of choice words including the included word are registered in the converted word field of the record, and if the fixed character string includes the included word, the processor processes the fixed character string as a temporary fixed character string that is subject to final selection by an operator from among the plurality of choice words.
16. A computer program product, tangibly stored on a machine-readable medium, comprising instructions operable to cause a programmable processor to perform operations comprising: receiving an input character string comprising a plurality of characters in the Roman alphabet, the input character string including a leading character; comparing the leading character to words included in a dictionary including records registering words formed from the Roman alphabet; iteratively comparing the leading character plus adjacent characters in the input character string to words included in the dictionary at least n times, wherein n is a positive integer, until the following conditions are satisfied: the leading character plus (n−1) adjacent characters matches a word in the dictionary, the leading character plus n adjacent characters does not match a word in the dictionary, and the leading character plus n+1 or more adjacent characters cannot match a word in the dictionary wherein the dictionary includes records registering the words, each record including a registered word field, a converted word field and a field indicating whether or not the registered word has an included word, and for records where the registered word has an included word, a plurality of choice words including the included word are registered in the converted word field of the record, and if the fixed character string includes the included word, the processor processes the fixed character string as a temporary fixed character string that is subject to final selection by an operator from among the plurality of choice words. 22. The computer program product of claim 16 , wherein the n th character adjacent to the leading character is a mark, the computer program product further comprising instructions operable to cause a programmable processor to perform operations comprising: making the leading character plus (n−1) adjacent characters a fixed character string; and displaying the mark after the fixed character string.