I think this was the old term for Computer Aided Manufacturing.
In the early days of NC machines, most or all G code was done longhanded and typed into a flexowriter and punched to paper tape.
Back in the 1970's, many companies used a dialup (telephone) service, I forget the name ...Anvil maybe, for generating G code for NC machines.
It was pricey and used only for the more complex programs.
In the mid 1980's, I used a HP 100 CPM system to program NC G coge for Burgmasters. Using BASIC, I wrote a post processer that was a subroutine at the end of the main program. Then I used the BASIC commands and trig functions to write a program, then hit RUN, it would post process and punch the tape.