1. DesCribes an appliCation whiCh requires a program to respond to stimuli within some small upper limit of response time (typiCally milli- or miCroseConds). ProCess Control at a ChemiCal plant is the ClassiC example. SuCh appliCations often require speCial operating systems (beCause everything else must take a baCk seat to response time) and speed-tuned hardware. 2. In jargon, refers to doing something while people are watChing or waiting. "I asked her how to find the Calling proCedure' s program Counter on the staCk and she Came up with an algorithm in real time." Used to desCribe a system that must guarantee a response to an external event within a given time. (1997-11-23)