To simultaneously enable input of a character string by a certain person and operation of a mouse cursor by the other person during the above input in OS of a multi-window system.

This method for simultaneously operating a mouse and a keyboard comprises a program linking a library in execution of the program, storing characters in one buffer according to a key event, outputting the buffer to one window, and inputting, in case that a character string of the buffer is instructed, it to a place instructed by the other program; a function A for hooking and processing the key with a function C; a function releasing the hooking and processing of the key event with the function C, and a shared library to be linked in the execution of the program, for transmitting a message after processing the key event hooked by the program linked therewith.