Quais "conceitos" foram usados antes dos sistemas operacionais?

Operating systems are the basis for modern computing, but before this, what was used in computer systems to make them work?

Early computers * ran one program at a time and programs loaded directly from paper tape with holes punched in it (for example). You would program the earliest computers * by setting a large set of on-off switches.

Colossus

*I am using the word ‘computer’ to mean the sort of device that exists nowadays in the billions. Of this vast number of computers, all but an insignificantly tiny number are digital electronic programmable computers with stored programs. I am sure the original question is not about how people with the job title ‘computer’ spent their working day. In between those two types of computer, there is a progression of interesting devices not covered in this answer.

History of Operating Systems (Source: Kent State University)

Operating systems have evolved through a number of distinct phases or generations which correspond roughly to the decades.

The 1940s – First Generation

The earliest electronic digital computers had no operating systems. Machines of the time were so primitive that programs were often entered one bit at a time on rows of mechanical switches (plug boards). Programming languages were unknown (not even any assembly languages). Operating systems were unheard of.

The 1950s – Second Generation

By the early 1950s, the routine had improved somewhat with the introduction of punch cards. The General Motors Research Laboratories implemented the first operating systems in the early 1950s for their IBM 701. The systems of the 1950s generally ran one job at a time. These were called single-stream batch processing systems because programs and data were submitted in groups or batches.

History of Operating Systems (Source: Wikipedia)

The earliest computers were mainframes that lacked any form of operating system.

Each user had sole use of the machine for a scheduled period of time and would arrive at the computer with a program and data, often on punched paper cards and magnetic or paper tape. The program would be loaded into the machine and the machine would work until the program was complete or crashed.

Programs could generally be debugged via a control panel using toggle switches and panel lights. It is said that Alan Turing was a master of this on the early Manchester Mark 1 machine and that he was already deriving the primitive conception of an operating system from the principles of the Universal Turing machine.