Memories      SAM (Sequential Access Memories) The Sequential nature means that you (or more likely the hardware involved) will have to read a long sequence of data in order to get to actually data wanted.    Hard-drives - R/W - Fast - Volatile - Magnetic based  USB-keys - R/W - Relative fast - Volatile - Flash ROM based  Floppy-drives - R/W - Slow - Volatile - Magnetic based - (If they still exists)  CD/DVD-Drives - R - Relative fast - Volatile - Optic storage (Can be written as well)  Backup-tapes - R/W - Slow - Volatile - Magnetic based     RAM (Random Access Memory) The Random Access nature means that its possible to get any data within a few (or single) clock-puls.    ROM (Read Only Memory)  Per definition must "real" ROM be factory product - but the term used generally  PROM - A one time user Programmable ROM  EPROM -  Erasable Programmable ROM  EEPROM - Electrically Erasable Programmable ROM  FlashROM -  Fast programmable and more advanced EEPROM technology (Link)    RWM (Read Write Memory) which most people call RAM  (Link1) (Link2) Static RAM can be considered based on D-F/Fs (Link3) Dynamic RAM - A "simple" way to implement memory - a bit stored with one capacitor and one FET transistor - A refresh circuit required. (Link4) Lots of new technologies can be found on the market like DDR, DDR2, EDO ect. Dual Port RAM - Basically a Static RAM with two sets of Address and Data-busses