real time

Also see real-time clock and real-time operating system.

Real time is a level of computer responsiveness that a user senses as sufficiently immediate or that enables the computer to keep up with some external process (for example, to present visualizations of the weather as it constantly changes). Real-time is an adjective pertaining to computers or processes that operate in real time. Real time describes a human rather than a machine sense of time.

In the days when mainframe batch computers were predominant, an expression for a mainframe that interacted immediately with users working from connected terminals was online in real time.