1. A text inputting device for inputting text to an information processing system comprising: (a) first means for inputting a string of characters of a first kind which designates a character of a second kind to be inputted to the information processing system in order to generate codes for the inputted string; (b) second means for generating in a first mode a code of the character of the second kind, including display means responsive to the codes from said first means for displaying candidate characters of the second kind which have a phonetic relationship to the text designated by the character string of the first kind, and operator-operable selection means for selecting one of the displayed candidate characters of the second kind to provide a code for said selected character of the second kind to said information processing system; (c) third means for generating in a second mode a code of a character of the second kind corresponding to the character string from said first means, wherein the character string is uniquely and predeterminedly assigned to the character of the second kind as a mnemonic code to provide the generated code of the character of the second kind to said information processing system; (d) fourth means for selecting either said first or second mode by alternatively connecting either said second or said third means to said first means, said fourth means being operated by the operator; and (e) fifth means cooperatively coupled to said second means for representing to the operator the mnemonic code of the character of the second kind selected by said operator-operable means to the operator, wherein in inputting a text to said information processing system, when a character of the second kind of which the mnemonic code is not known by the operator appears in the text, said fourth means is activated to enable said second means to operate in said first mode, and when a character of the second kind of which the mnemonic code is known by the operator appears in the text, said fourth means is selectively activated to enable said third means to operate in said second mode.