Abstract: Point of sale apparatus wherein a general purpose computer is utilized in emulating the functions of an integrated POS system. A general purpose computer is employed with a cash register specific keyboard to provide a broad range of computational and data handling capabilities for the apparatus. To perform in conjunction with the general purpose computer for its general computing function, a typewriter-type keyboard is employed with the apparatus. A prioritized protocol is developed between the two keyboard functions giving operational priority to the latter keyboard. To achieve a necessary reaction to cash register keying operations, a device driver program is positioned at a high priority level in the BIOS area of memory of the general computer to develop a vector interrupt deriving a jump address approach to the execution of cash register key function commands.