A short review of read-only memories

The history of read-only memories in telephone and digital-computer systems is briefly surveyed and their similarity to logic circuits demonstrated by reference to the diode matrix. A description is given of the principles of operation and important characteristics of the following types of read-only memory: capacitor matrix, mutual-inductance matrix, transformer (Dimond ring) type, square-loop ferrite-core matrix, permanent-magnet twistor matrix, flying-spot store and electroluminescent matrix. These memories are briefly compared.