the screen 12b and the operation of the kbes is transparent to the application program and requires no modification to the application program or special procedures for the user additionally the pen 14 may continue to be used with the application program while also being used to supply keystroke data when the computer is in the keyboard emulation mode for example the pen 14 may emulate a mouse when used to interact with the application program graphics displayed in the top segment 12t and be used to enter keystroke data by touching the display on the bottom segment 12b a block diagram of the kbes is depicted in fig2 referring now to fig2 a system processor 20 video control system vcs 22 system memory smem 24 overlay controller 26 and keyboard scan code register 28 having an output connected to an interrupt line 28i are coupled to the system data bus dbus 30 the vcs 22 is connected to the screen 12 by video signal and control lines 32 and 34 the overlay controller 26 is connected to the screen overlay by electrical interconnection lines 36 and is also connected to the conductive pen 14 by the wire 16 during the keyboard emulation mode a bios 24a application program 24b terminate and stay resident keyboard emulation program kpep 24c and look up table lut 24d are stored in the smem 24 the operation of the system of fig2 will now be described with reference to the flow chart of fig3 when the keyboard emulation mode is initiated the special trs terminate and stay resident keyboard emulation program kbep 24c is called the kbep 24c adjusts the vcs 22 to place the.