Core memory unit of four matrices each with 64 memory cores, maker: Zuse KG/Neukirchen, approx. 1965, 33.0 × 17.9 cm. KIT, Scientific Computing Center.
Core memory, with its grid-like structure, is a precursor to modern computer hard disks. In use from the mid-1950s for about 20 years, this storage medium employed ring-shaped ferrite cores suspended at the intersections of wires. These cores could be magnetized by a brief flow of current, making them suitable for information storage. By dividing the current directed to a specific ring to the two crossing wires, the individual storage units could be precisely controlled. Each ring could be either magnetized or demagnetized, representing a single bit of information. Characters were encoded using sequences of several bits, often 8, meaning that even a single letter required multiple memory cores. The intricate design of the core memory and visibility of the memory units to the naked eye make it clear that this was a complex and costly technology, offering relatively modest storage capacity compared to modern technology. In 1965, a Zuse computer at the Institute of Applied Mathematics, at that time located in the architecture building of Karlsruhe Polytechnic, was upgraded with core memory. These memory units, recallable in less time compared to punched tape, were needed for information that was supposed to be particularly rapidly available in a running program. During the installation process, technicians placed the core memory units in the hallway of the architecture building. The sight of these grid elements apparently proved to be so intriguing to architecture students that several of the expensive components went missing. Fortunately, after several appeals, including an announcement in the cafeteria, all the missing components were fortunately returned. kn