An interlocking architecture for a software interface and a bar code scanner. Upon power-up, a handshaking operation is performed between a scanner (1600) having a scanner processor (2600) and a computer processor (2612) of a computer (302) based upon the code stored in the NV memory (2602) of the scanner (1600) and a unique code associated with the software interface running on the computer (302). A wedge (1608) is provided as an interface mechanism for the scanner (1600) and a keyboard (1610) to a keyboard port (2500) of the computer (302). The handshaking occurs through the wedge (1608) via a keyboard interface (2610) to the processor (2600) such that a successful handshake directs the processor (2600) to engage a switch (2604) which enables power to a sensing head (2606) for read optically encoded information. The software interface operates from a computer memory (2614) associated with the processor (2612) whereby an unsuccessful handshake using unique number of the software interface by the processor (2612) sends a disabling signal though the keyboard circuit (2618) through the wedge (1608) to the scanner processor (2600) to disengage the switch (2604) to drop power to the sensor head (2606). The handshaking operation is performed on a regular basis during system power-up to ensure that the original software interface and scanner (1600) are still in use.