A room full of computers, as they were called back then.
Not the machines, the people.
When I worked FDC for 105 and 155 gun lines in the Marines in the early ‘80s, I was the guy who handled the horizontal chart and my buddy Ron was the “computer”. He was fast with the books. It wasn’t long after that time that the Marines went to a Texas Instruments calculator with a special template the fit over the top.