1960 to 1969: The Rise of Business Computers and Business Software - The Technical and Social History of Software Engineering - page 126

Computers and Software in Space
On July 20, 1969, the Apollo 11 spacecraft landed Neil Armstrong and Buzz
Aldrin on the moon. This was one of the greatest scientific achievements in human
history.
The Apollo spacecrafts pioneered the use of digital computers and software for
the space program. The physical computer used on the Apollo program was among
the first to combine integrated circuits and low-power transistors. It was named
the Apollo Guidance Computer (AGC).
The AGC utilized a special kind of read-only memory (ROM) called a core
rope . A magnetized strand passed through hollow cores. Up to 64 separate wires
could pass through a core, and each carried software information. The advantage
of core ropes was high-density storage—about 18 times more data than conven-
tional magnetic cores could hold.
These core ropes were actually woven by female seamstresses. This gave rise
to a slang term for the memory of "LOL," or "little old lady."
Although the Apollo team included many famous engineers and scientists,
Charles Stuart Draper was one of the Apollo computing pioneers. The famous
MIT lab in Cambridge, Massachusetts, is named for him.
IBM was also a participant in the Apollo program, and the famous IMS data-
base was first created for the Apollo program, but it was also marketed commer-
cially.
The Apollo software was programmed using both an assembly language and an
interpreted language. A special real-time, multitasking operating system was de-
veloped for the Apollo program. While the Apollo computer was slow and limited
compared to today's computers, it was a great step for computing, just as landing
on the moon was a great step for mankind.
Alarmingly, during the descent to the moon, a number of error conditions and
error messages appeared, indicating computer or software problems. Apparently,
too many tasks were executing concurrently and exceeding the system capacity.
Fortunately, the software had priority scheduling algorithms and it was possible
to eliminate low-priority tasks so that the actual guidance of the descent operated
perfectly. One of the Apollo guidance controllers, Steve Bales, received a Pres-
idential Medal of Freedom award in recognition of his successfully ensuring the
Apollo landing.