they needed a way to hardwire their computer programs and coding so it could not be erased during a loss of power. The system they devised was called rope memory, with software being carefully woven through wire ropes to create physical distinctions between "1s" and "0s," as in the binary computer code.

"Informally, the programs were called ‘ropes’ because of the durable form of read-only memory into which they were transformed for flight, which resembled a rope of woven copper wire,” said MIT engineer Don Eyles. “For the lunar missions, 36K words of ‘fixed’ (read-only) memory, each word consisting of 15 bits plus a parity bit, were available for the program.”

These tiny ropes allowed NASA to store an insane amount of data needed for basic flight procedures without taking up too much room on the already packed ship. The process to weave the software into the ropes was so tedious and slow, it would easily take months to create just one program.

Eyles says that with core rope memory, plus the Apollo’s on-board RAM (erasable) memory, NASA landed the lunar module on the moon with just about 152 kilobytes of memory with running speeds of 0.043 megahertz.