bubble memory cathode ray tube ddr sdram delay line memory drum memory dynamic random access memory eeprom eprom electrical resistance england ferranti mark i ferroelectric ram flash memory frederic calland williams ias machine mit press magnetic core memory magnetoresistive random access memory manchester small-scale experimental machine manchester university press mellon optical memory memory refresh nano-ram non-volatile memory phase-change memory phosphor plated wire memory programmable metallization cell programmable read-only memory racetrack memory radar read-only memory regenerative capacitor memory resistive random-access memory sonos secondary emission selectron tube static random access memory tom kilburn twin transistor ram twistor memory victoria university of manchester volatile memory z-ram