Definition: early memory

Similar to a CRT, electrostatic storage tubes used in the first Whirlwind computer in 1950 held a whopping 256 bits each. The bits were "painted" on the surface of the tube, and their electrostatic charges determined their content. See Williams tube. (Image courtesy of The MITRE Corporation Archives.)

The contents of memory were kept active by oscillating through tubes filled with liquid mercury. The UNIVAC I had seven tubes, and each was divided into 18 channels for a total of 1,000 words. A word held two instructions, 12 characters or 11 digits plus sign. See delay line memory. (Photo taken courtesy of The Computer History Museum.)

This rotating magnetic drum from an IBM 650 was introduced in 1954 and held up to four thousand 10-digit words. The program was read from magnetic tape and written onto the drum. Today, that much memory today would fit on the head of a pin with room to spare (see IBM 650). (Image courtesy of the Hagley Museum and Library.)

Core memory came out in the early 1950s and was widely used for two decades. The direction of the magnetic energy in the core determined the 0 or 1. This core plane, which held 256 bits, replaced the electrostatic tubes in the Whirlwind I. See core storage. (Image courtesy of The MITRE Corporation Archives.)

Over the years, magnetic cores became so small that a thousand of them would look like a tiny pile of dust. Using a microscope, workers in third-world countries were hired to string them together. About 30" high, this Dataram module provided 16KB of RAM for a Data General minicomputer in 1967. See core storage.