Mouse emulation includes two modes, a host mode in which the pointer behaves as the pointer of the host system and an emulating mode in which the pointer behaves as the pointer of the target system being emulated. The display of the target system appears in an emulation window within the host system display. The user can switch from host mode to emulating mode by clicking a mouse key when the pointer is located in the emulation window which also serves to make the emulation window the input focus for receiving user input signals from the keyboard. The user can switch from emulating mode to host mode by depressing a STOP key, a keystroke which need not be provided to the emulator because it would not be provided to the target system's CPU. Mouse related data is transferred to the emulator through a data structure in a reserved memory space which a mouse application does not access, such as the BIOS area if an IBM PC is being emulated. A mouse driver which provides standard responses to service requests from the application retrieves this data from the data structure, making hardware ports or software emulating or bypassing such ports unnecessary.