Accounting machine processor

Claim 1

An electronic processing unit for a mechanical accounting or billing machine, said processing unit receiving address containing instructions from the mechanical machine for entering data therein and recalling data therefrom comprising: a. a memory including 1. a plurality of registers, and 2. settable means associated with said registers for indicating the storage of different numbers of constants in the associated memory registers and for designating selected ones of said registers as read-only memories, said settable means causing tag bits to be placed into said selected registers, said tag bits causing said selected registers to be treated as read-only memories, b. an arithmetic unit coupled to said memory for operating on data received from the mechanical machine in conjunction with data stored in a register of said plurality of registers in said memory designated by the address contained in the instruction and for storing the result of the operation in the addressed designated register, and c. controlling means coupled to said mechanical machine and said settable means of said memory for controlling the storage of data in said memory, said controlling means being responsive to an instruction from said mechanical machine and to said settable means for recalling a selected one of the constants stored in a selected designated register of said plurality of memory registers to said mechanical machine and responsive to the designation of one of said plurality of memory registers by said settable means as a read-only memory for preventing any modification of the contents of the designated register, and responsive to a reference code received from the mechanical machine for substituting an address contained in said reference code for the address associated with the next instructions received from the mechanical machine.