1. A text input support system for supporting input of text including a plurality of words separated from each other with spaces, the system comprising: a keyboard for inputting a character string in the Roman alphabet; a display device for displaying the input character string; a storage device for storing a program and data; a processor for processing the character string in the Roman alphabet input by the keyboard in accordance with the stored program; and a dictionary including records registering words in the Roman alphabet that can be used for text input, the dictionary being stored in the storage device as data; wherein: the processor compares the input character string in the Roman alphabet with words registered in the dictionary one-by-one character starting from a leading character, memorizes a word that is identical to the input character string, makes the word that was identical to the input character string in a previous iteration a fixed character string upon determining that no possibility exists that the input character string will be identical to another word registered in the dictionary, and adds a space after the fixed character string so as to separate the character string from a subsequent input character string; records included in the dictionary each include 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.