What is Real-Time?
• What is hard real-time? • What is soft real-time? • Who needs real-time? hard real-time? soft real-time? • How do you characterize and specify real-time performance? (In other words, what specifications should be used to objectively compare real-time OSes?)The replies from the panelists were both thoughtful and instructive. If you have the time and interest, I strongly suggest reading each panelist’s answers. Use the following links . . . • David Beal, Product Marketing Manager, Lineo — response • Mitch Bunnell, CTO/cofounder, LynuxWorks response • Steve Furr, Senior Software Developer, QNX Software Systems — response • Douglass Locke, VP Technology, TimeSys — response • Jim Ready, CEO and founder, MontaVista — response • Victor Yodaiken, CEO and cofounder, FSMLabs — response • Myron Zimmerman, CTO and founder, VenturCom — responseSo . . . What is real-time, and who needs it? After carefully studying the answers from our panel of real-time experts, I’ve put together composite a
Real Time Displaying/Recording is defined as displaying or recording a video sequence at 30 frames per second. At this rate the individual frames are indistinguishable by human eyes and therefore it is referred as continuous streaming. However, a more expensive DVR-card, computer and a hard disc with a larger capacity is required to carry out surveillance monitoring at such a high standard. Under normal conditions 3-5 frames/sec is a reasonable number.
Many developers typically think that “real-time” means “really fast” as in moment-to-moment interaction with the system. While we work to keep Java RTS fast, real-time in the RTSJ context means “the ability to reliably and predictably respond to a real-world event”. So “real-time” is more about timing than speed, per se. The ability to program a real-time solution means that developers need the appropriate support from the system in order to reason in a temporal fashion. Said more formally: • Real-Time application development requires: An API set and semantics which allow developers to correctly reason about and control the temporal behavior of applications. • RTSJ /Java RTS provides: An API set, semantic Java VM enhancements, and JVM-to-OS layer modifications which allow Java developers to correctly reason about and control the temporal behavior of Java applications.
In computing, real-time refers to a time frame that is very brief, appearing to be immediate. When a computer processes data in real time, it reads and handles data as it is received, producing results without delay. For example, a website that is updated in real-time will allow its viewers to see changes as soon as they occur, rather than waiting for updates to be visible at some later date. A non-real-time computer process does not have a deadline. Such a process can be considered non-real-time, even if fast results are preferred. A real-time system, on the other hand, is expected to respond not just quickly, but also within a predictable period of time. A good example of a real-time computer system is a car’s anti-lock break system. An anti-lock brake system is expected to release a vehicle’s brakes, preventing dangerous wheel locking, in a predictably short time frame. Unfortunately, there are times when real-time systems fail to respond as desired. A Real-time process fails when i
