It's kind of archaic, now, but back in the day you used to have a computer that filled a whole room and there would be an operator in charge of compiling and running jobs, returning (printed) output, managing user accounts, resources, backups.
Sort of analogous to a system administrator on multiple smaller computers used as servers, or the IT guy on personal computers used for work, but much more direct, in that they would actually be the one who operated the computer. Users submitted typed programs that would be input into punchcards and run as a batch, or run on a scheduled basis.
Systems Operator: Maintains and runs systems, often works from runbooks, or automated UI's; does not write code, works within the constraints set by Administrators. Level 2 Helpdesk.
Systems Administrators: Responsible for writing documentation, addressing the needs of monitoring. Usually the person writing runbooks and scripts, works closely with a Helpdesk and their needs, automates recurrent problems. Level 3 Helpdesk.
Systems Engineer: Responsible for architecture, understanding complex systems, working on new projects, making Systems Administrators lives easier. Working with Architects on upcoming projects, likely designed and built the logging solution, database migration systems, job control systems.
Systems Architect: Same as a systems engineer except focused on business needs instead of technical ones. Usually works on a higher level of abstraction, often works across many teams to gather needs.
This was a book that was "old" when I read it in 2007, so, obviously this no longer reflects reality (if it ever did).
You would write down the program you want to get executed or punch it on punch cards.
The only people who could actually operate the computer were... the operators. These people (mainly women) would transfer the program to the computer, execute it and then transfer the answer back to the requestor.
This survived into later because an admin on the server is was the only person who could actually operate the server. The rest can only within whatever rights the admin gave them, but for any important operation (like adding a user) you still needed the admin (operator) to take action.
The work was:
* Putting paper on printers * Taking paper off printers * Decollating the paper that came off printers * Putting tapes into tape drives * Taking tapes out of tape drives
The slacking was
* Going to the pub before it closed on night shift * Having sword fights with the plastic swords we used to cut paper * Finding an unlocked office and using the phone to call party lines
The work highlights were:
* Going to a vault and back flanked by security guards to get the Queen's tape * Printing bank statements of the rich and famous (I've seen Mick Jagger's bank account)
Also, in my experience 'computer operators' weren't really 'sysadmins' they were more like automated job scheduling services. Follow the run book, run batch jobs, check for errors sort of thing
Source: I've held all 3 positions at one time or another.
You could train to be a computer programmer, operator, or technician. Seems like a standard term of art for the 1970s.