system
A chat on subreddit /r/pcmasterrace
human
Can confirm. My stepmom was a mainframe operator for NADEP at a Marine Corps Air Station in the late '80s - mid '90s. They were still using IBM 360 Series mainframes that dated back to the mid - late '60s.
gpt
The programmers behind a lot of those sorts of systems were making bank during the Y2K crisis, some were coming out of retirement to fix COBOL software and charging like $10k a day for their time!