page_title: Apollo Guidance Computer
section_title: Other registers
hierarchical_section_title: Apollo Guidance Computer / Design / Other registers
caption_attribution_description: English: Apollo Guidance Computer with Display and Keyboard DSKY (above) on display at the Computer History Museum.
context_page_description: The Apollo Guidance Computer is a digital computer produced for the Apollo program that was installed on board each Apollo command module and Apollo Lunar Module. The AGC provided computation and electronic interfaces for guidance, navigation, and control of the spacecraft.
  The AGC has a 16-bit word length, with 15 data bits and one parity bit. Most of the software on the AGC is stored in a special read-only memory known as core rope memory, fashioned by weaving wires through and around magnetic cores, though a small amount of read/write core memory is available.
  Astronauts communicated with the AGC using a numeric display and keyboard called the DSKY. The AGC and its DSKY user interface were developed in the early 1960s for the Apollo program by the MIT Instrumentation Laboratory and first flew in 1966. The AGC was the first silicon integrated circuit based computer. The computer's performance was comparable to the first generation of home computers from the late 1970s, such as the Apple II, TRS-80, and Commodore PET.
context_section_description: The AGC had additional registers that were used internally in the course of operation:
caption: DSKY and AGC prototypes on display at the Computer History Museum. The AGC is opened up, showing its logic modules.
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