Time-Sharing Environment
TELNET was designed at a time when most operating systems, such as UNIX, were
operating in a time-sharing environment. In such an environment, a large computer
supports multiple users. The interaction between a user and the computer occurs
through a terminal, which is usually a combination of keyboard, monitor, and mouse.
Even a microcomputer can simulate a terminal with a terminal emulator.
In a time-sharing environment, all of the processing must be done by the central
computer. When a user types a character on the keyboard, the character is usually sent
to the computer and echoed to the monitor. Time-sharing creates an environment in
which each user has the illusion of a dedicated computer. The user can run a program,
access the system resources, switch from one program to another, and so on.