Abstract: A computer is programmed to generate addresses for recordation in the address track of a rotating disc file memory at predetermined intervals of space. Clock pulses are generated synchronized with the rotation of the disc. The clock pulses are applied to the computer to time the execution of the program so the addresses generated by the computer are synchronized to the rotation of the disc. The generated addresses are recorded in the address track of the disc as it rotates. A clock pulse counter set by instructions of the program controls the spacing between address data items. Address data can be recorded in the address track at different densities with the same program. The computer memory has a replaceable read-only section in which the program is stored. Different address formats are generated by changing the read-only section.