Abstract: A program processing system including a program input device for entering optional programs for performing an optional function, an optional-program memory for storing the optional programs, a standard-program memory which stores a standard program for performing a basic function; a commanding device for designating one of the optional programs, for execution of the designated optional program, and a controller for retrieving the designated optional program from the optional-program memory, to perform the corresponding optional function, if the designated optional program is stored in the optional-program memory, the control means retrieving the standard program from the standard-program memory, to perform the basic function, if the designated optional program is not stored in the optional-program memory means.

Abstract: In a text processing device, provided is an improved tabulation function. The vertical positions of horizontal ruled lines dividing two rows are calculated based upon the intervals existing between these columns. If the row interval is expanded or changed, the horizontal ruled lines remain consistent in a predetermined relationship with a character string.

Abstract: A power amplifier which has a muting circuit bringing the power amplifier into a muting condition when an excessively large input signal is applied. The power amplifier comprises a preamplifying stage and a power amplifying stage. The preamplifying stage includes at least one transistor for driving the power amplifying stage. The collector of the transistor is coupled to one power source terminal. The emitter of the transistor is coupled to the other power source terminal through an electronic switch, and to the first power source terminal through a resistor. The electronic switch selectively connects the emitter of the transistor to one of the power source terminals.