Editing Apollo Guidance Computer (section)

{{short description|Guidance and navigation computer used in Apollo spacecraft}}
{{Infobox computer hardware
| name         = Apollo Guidance Computer
| image        = Agc view.jpg
| caption      = Apollo Guidance Computer and DSKY
| invent-date  =
| invent-name  = [[Charles Stark Draper Laboratory]]
| manufacturer = [[Raytheon]]
| designfirm   =
| introduced   = {{Start date and age|1966|08}}
| discontinued = {{Start date and age|1975|07}}
| cost         =
| type         = {{ubl|[[Avionics]]|Guidance computer}}
| processor    = Discrete [[silicon]] [[integrated circuit]] (IC) chips ([[Resistor–transistor logic|RTL]] based)
| frequency    = 2.048 MHz
| memory       = {{ubl|15-bit wordlength + 1-bit parity|2048 words [[Random-access memory|RAM]] ([[magnetic-core memory]])|36,864 words [[Read-only memory|ROM]] ([[core rope memory]])<ref>{{citation |url=https://www.ibiblio.org/apollo/assembly_language_manual.html |title=Programmer's Manual, Block 2 AGC Assembly Language |access-date=2018-08-27}}</ref>}}
| ports       = DSKY, IMU, Hand Controller, Rendezvous Radar (LM), Landing Radar (LM), Telemetry Receiver, Engine Command, Reaction Control System
| power        = 55 W<ref name="Hall-1996" />{{rp|120}}
| weight       = {{convert|70|lb|kg|abbr=on|adj=on}}
| dimensions   = {{cvt|24|x|12.5|x|6.5|in|cm}}
|language=AGC Assembly Language
}}

The '''Apollo Guidance Computer''' ('''AGC''') was a [[digital computer]] produced for the [[Apollo program]] that was installed on board each [[Apollo command module]] (CM) and [[Apollo Lunar Module]] (LM). The AGC provided computation and electronic interfaces for guidance, navigation, and control of the spacecraft.<ref>{{cite web|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090016290.pdf|title=Apollo Guidance, Navigation and Control Hardware Overview|date=January 2009|last1=Interbartolo|first1=Michael}}</ref> The AGC was among the first computers based on [[silicon]] [[integrated circuit]]s (ICs).<ref name=":2">{{Cite web |date=2025 |title=1962: Aerospace systems are the first applications for ICs in computers |url=https://www.computerhistory.org/siliconengine/aerospace-systems-are-first-the-applications-for-ics-in-computers/ |url-status=live |access-date=March 13, 2025 |website=Computer History Museum}}</ref><ref name=":3">{{Cite web |last=tluong |date=2019-07-17 |title=Silicon Chips Take Man to the Moon |url=https://computerhistory.org/blog/silicon-chips-take-man-to-the-moon/ |access-date=2025-03-31 |website=CHM |language=en}}</ref> The computer's performance was comparable to the first generation of [[home computer]]s from the late 1970s, such as the [[Apple II]], [[TRS-80]], and [[Commodore PET]].<ref>{{cite web |date=11 March 2017 |title=How did the Apollo flight computers get men to the moon and back ? |url=http://curious-droid.com/214/apollo-flight-computers-get-men-moon-back/}}</ref> At around 2 cubic feet in size, AGC held 4,100 IC packages.<ref name=":3" /> 

The AGC has a 16-bit [[Word (computer architecture)|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 core]]s, 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 (for "display and keyboard", pronounced "DIS-kee"). 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.<ref>{{cite web |url=https://history.nasa.gov/computers/Ch2-5.html |work=Computers in Spaceflight: The NASA Experience |author=James E. Tomayko |title=The Apollo guidance computer: Hardware |publisher=NASA |date=1988 |archive-url=https://web.archive.org/web/20231229162736/https://history.nasa.gov/computers/Ch2-5.html |archive-date=December 29, 2023 |url-status=dead}}</ref> The onboard AGC systems were secondary, as NASA conducted primary navigation with mainframe computers in Houston.<ref name=":1" />