How did early time-sharing systems allow multiple users to share one computer?

Early time-sharing systems allowed multiple users to interact with a single central processing unit (CPU) by rapidly switching between different programs. Because the CPU operates at speeds significantly faster than peripheral equipment like keyboards and printers, it could process discrete tasks for multiple users in sequence.12

To manage this, the operating system allocated a limited slice of CPU time to each user's process. Once a process's time expired, the system would suspend it, save its state, and switch to the next user, repeating this cycle so quickly that the system appeared to provide instantaneous, simultaneous access to everyone connected via remote terminals.21

This method was developed in the late 1950s and early 1960s to improve the efficiency of expensive computing hardware, moving away from "batch processing," where users had to wait hours for results. Early systems, such as the Compatible Time-Sharing System (CTSS), required careful control by the operating system to ensure that users' programs did not interfere with one another, a challenge eventually addressed through techniques like virtual memory.132