PURPOSE: To ensure a smooth input operation in each mode by applying the prescribed control to the transmission a key number to a specific key input when a mode flag shows a standard mode.

CONSTITUTION: A controller 25 of a memory board 2 connected to a main board 1 is connected to a keyboard 50 via a cable. Then an English word MS- DOS and Japanese words MS and DOS are supplied to a hard disk device of a RAM 21 in two different partitions. Then a system switching command is sued to attain the mutual changeover between both languages. At the same time, a Japanese mode flag 52 is added to a controller 51 of the switchboard 50. When a pressed key is a KANJI (Chinese character) designating key or a KANA (Japanese syllabary) designating key which is exclusive for a Japanese language mode, the relevant key number information is sent to the controller 25 under the control of a CPU 11 when a flag 52 is set. While the transmission of said information is inhibited when the flag 52 is not set.