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:: The EIA RS standards, which governed members of the EIA, were essentially copies of earlier AIA National Aerospace Standards: NAS 943 (Straight Cut) and NAS 955 (Contour Cut). NAS 943 was approved in 1960 (as per the AIA Annual Report, available online).
:: Those standards are predominately based on the two leading Numerically Controlled mills during the APT work: the Giddings & Lewis mill (trademarked as the Numericord) which used a combination of General Electric and Concord Controls controllers. The second system was the Kearney & Trecker mill, which used a Bendix controller. Both machines had detailed papers published at the Eastern Joint Computer Conference in December 1957 (proceedings available online). The Bendix solution used "R-codes" to describe operational modes (essentially G-codes) and another set to describe auxiliary on/off functions (essentially M-codes). The Giddings & Lewis system used "X-codes" which also described operational modes and auxiliary on/off functions. These are the X-codes described in the APT flowcharts. The assertion that these were the two leading NC mills in the mid-50s can be found in <i>Forces of Production</i> by David F. Noble. The same book contains significant content as to why Bendix became the preferred solution during the standardization process.
:: The X-codes are better documented in US patent 2963137 "Controls for a typewriter and associated apparatus" (the patent title is somewhat misleading - this is a numerical control patent). The patent assignee is Giddings & Lewis, but the four inventors (McDonough, Susskind, Grossimon, and Lee) were all MIT staff attached to the Servo Lab. Giddings & Lewis poached the entire numerical control staff (with the exception of Susskind) to form Concord Controls at the beginning of 1956.
:: The Bendix R-codes were encoded on punch tape in their own special block, so there was never an appearance of an alphanumeric code, such as "R00". The Giddings & Lewis X-Code, however, appeared exactly as G-Code would later be used. There is no relationship between the operational code numbers between X-Code and the later G-code. It's unknown if the same can be said for the auxiliary functions, as they are deliberately not documented in the 1957 paper, nor the 1956 patent - other than the Program End function which was encoded as "X00", the same as the later "M00".
::[[User:Alvonruff|Alvonruff]] ([[User talk:Alvonruff|talk]]) 15:17, 16 September 2021 (UTC)
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