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commercial real time operating system

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Parth86

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If window and unix are not a real time operating then what is meaning of " unix as real time operating systema, window as real time operating system
look at this pdf file
there are two statement unix as real time operating system and window as real time operating system

I don't understand what is the meaning of both statement in this pdf file
can someone tell me what is this ?
 

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It really comes down to your definition of "real time" with respect to your expectations of the timely functioning of the entire computing system (hardware plus software).

Let's say you coding for a word processing (WP) program for Windows Vista, as I am doing this moment (essentially an OS based on Windows NT). The time intervals one would expect the system processor (the CPU) to need to react to user input (typing) would be on the order of 10s or 100s of milliseconds (the speed of the typist hitting keys).

So long as there were no significant delays between the hitting of a key and the placement of a character on the screen (no latency) then the system could be considered "rear time" - you hit a key - a letter appears on the screen "instantly".

Now imagine your coding for a program that must monitor the activities of of a military jet aircraft (an enormously complex system). Consider the 100s or even 1000s of sensor inputs (engine, airfoils, radar, weapon systems, pilot, environmental, etc.) and processors outputs that the OS must cope with to assure the timely functioning of ALL systems to keep that aircraft at peak performance. That's a lot of "mouths at the watering trough" clamoring for priority. "Real time" is on the order of, realistically, micro seconds and even conceivably nanoseconds. A completely different definition of "instantly".
 
The short version is that "real time" is all about deadlines: Whether a task will produce the correct output within a certain time every time it is launched. Now you can have both "soft" and "hard" real-time. "Soft" means you can miss deadlines occasionally (human-machine interface, Quality-of-service) without disaster occurring. "Hard" means if you miss a single deadline, you're boned. Windows and Linux can fall under the "soft" category depending on the kernel version and the application, but for hard real-time, neither is a good choice (I've seen it first-hand in Linux, don't know about Windows but I imagine it's a similar story).
 
It really comes down to your definition of "real time" with respect to your expectations of the timely functioning of the entire computing system (hardware plus software).

Let's say you coding for a word processing (WP) program for Windows Vista, as I am doing this moment (essentially an OS based on Windows NT). The time intervals one would expect the system processor (the CPU) to need to react to user input (typing) would be on the order of 10s or 100s of milliseconds (the speed of the typist hitting keys).

So long as there were no significant delays between the hitting of a key and the placement of a character on the screen (no latency) then the system could be considered "rear time" - you hit a key - a letter appears on the screen "instantly".

Now imagine your coding for a program that must monitor the activities of of a military jet aircraft (an enormously complex system). Consider the 100s or even 1000s of sensor inputs (engine, airfoils, radar, weapon systems, pilot, environmental, etc.) and processors outputs that the OS must cope with to assure the timely functioning of ALL systems to keep that aircraft at peak performance. That's a lot of "mouths at the watering trough" clamoring for priority. "Real time" is on the order of, realistically, micro seconds and even conceivably nanoseconds. A completely different definition of "instantly".
thanks for reply . have you read this PDF file. I am asking about two statement unix and window as real time operating system
 
Yes, I read it. Much lengthier (and in greater detail) description of what I posted...

If window and unix are not a real time operating...

On what do you base post#1 lead-in statement above?

The phrase "real time operating system" is utterly relative to the task(s) placed upon the OS and its ability to perform those tasks in a manner that does not significantly interfere with subsequent (or worse, simultaneous) tasks being performed in an equally timely fashion.

Both Windows and Unix can do this, but obviously only within well defined limitations of, 1. hardware clock and configuration limitations and, 2. software design.
 
I don't think there's any functional difference between OS and RTOS. RTOS is just a historical word often used for OSes designed for embedded processors.
 
vead,

You might want to investigate OS kernels (in all their many permutations), as they are the final software to hardware "link" that determines/controls CPU/Memory/IO functional time sharing.

And, frankly, I think "real-time", in this context, is a term that is so fluid (that is, subject to any observer's biases) that it will never be defined to the degree that no further definitions are possible.
 
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