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Rope memory from the Apollo Guidance Computer
Photo detail of a 16Kb rope core memory board from a 1974 computer
Core rope memory test sample from the Apollo program

Core rope memory is a form of read-only memory (ROM) for computers. It was used in the UNIVAC I (Universal Automatic Computer I) and the UNIVAC II, developed by the Eckert-Mauchly Computer Corporation in the 1950s, as it was a popular technology for program and data storage in that era. It was later used in the 1960s by early NASA Mars space probes and then in the Apollo Guidance Computer (AGC)[1] and programmed by the Massachusetts Institute of Technology (MIT) Instrumentation Lab and built by Raytheon.

Software written by MIT programmers was woven into core rope memory by female workers in factories. Some programmers nicknamed the finished product LOL memory, for Little Old Lady memory.[2]

Memory density

By the standards of the time, a relatively large amount of data could be stored in a small installed volume of core rope memory: 72 kilobytes per cubic foot, or roughly 2.5 megabytes per cubic meter. This was about 18 times the amount of magnetic-core memory (within two cubic feet).[citation needed]

Data units per cubic foot Data units per cubic meter
Bytes Bits Bytes Bits
Core rope ROM 72 KB 576 Kbit ~2.5 MB ~20 Mbit
Magnetic-core RAM 4 KB 32 Kbit ~140 KB ~1 Mbit


  1. ^ "Software as Hardware: Apollo's Rope Memory". Retrieved 29 Sep 2017.
  2. ^ Directed and Produced by: Duncan Copp, Nick Davidson, Christopher Riley (2008-07-07). "The Navigation Computer". Moon Machines. Episode 3. 22:40 minutes in. Science Channel.