what is real time operating system ?

If you want those two things to happen at the same time, then none can be executed first, but both have to be running at the same time.
For this the multitasking OS lets one process run for a while, then lets the other process run for a while. This time ususally is somewhere around 1-10ms.
From the user point of view it seems like both are running at the same time, but in reality they are taking turns to use the cpu.

The very first multi-finder for the mac OS, the application itself limited the amount of time it ran. Of the top of my head, I'm not sure what this is called.

Preemptive multitasking is generally when a timer preempts what was running and the scheduler runs the next process.

It's not that simple because when a program runs, it might need to "wait for input" or wait for a disk block to be read. So, some other process can run while that's happening.

One of the easiest programming languages to write code that can parallel process is LabView or G. The code in inherent that way. You have to do things to make it execute sequentially. Programs can develop "race conditions" just like logic gates can.

The programs are "wired", by connecting graphical icons together. The routine or what's called a "Virtual instrument" executes when all of the data is available to it,

The initial versions; the first I used was 2.2 was a real mess with error handling.

QOS or quality of service is a way for an Internet switch to prioritize data. We'd like video and voice to run without gaps. Retrieving a web page can wait. Buffering the audio data is a simple way of starting the process.

kubeek said:

If you want those two things to happen at the same time, then none can be executed first, but both have to be running at the same time.
For this the multitasking OS lets one process run for a while, then lets the other process run for a while. This time ususally is somewhere around 1-10ms.
From the user point of view it seems like both are running at the same time, but in reality they are taking turns to use the cpu.

Click to expand...

That is called multitasking. Multitasking and real time operating systems are two different things. They are related, but a different thing.

Real time operating system is something that can guarantee precise timing. And missing that timing is a horrible system error.

Re ATM's - I am told they all run XP. Now that's scary...

misterT said:

Real time operating system is something that can guarantee precise timing. And missing that timing is a horrible system error.

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You cannot guarantee precise timing. If you have two events happening at the same time, one of them will be, unavoidably, delayed.

misterT said:

That is called multitasking. Multitasking and real time operating systems are two different things. They are related, but a different thing.

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Of course, but he was asking how multitasking is done. I should have mentioned that it has nothing to do with the OS being realtime or not.

throbscottle said:

Re ATM's - I am told they all run XP. Now that's scary...

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That doesn´t matter at all, as long as they are run on a standalone network with no I/O access to the outside world. They could very well run on W95 and it still would not matter, since you can´t do anything with a touchscreen and a few buttons.

kubeek said:

Of course, but he was asking how multitasking is done.

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The topic says "what is real time operating system" not "what is multitasking".

NorthGuy said:

You cannot guarantee precise timing. If you have two events happening at the same time, one of them will be, unavoidably, delayed.

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Yes.. and that is the challenge of "real time operating system"

misterT said:

The topic says "what is real time operating system" not "what is multitasking".

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Topic maybe, but the question was directly aimed at multitasking.

multitasking - the ability to execute more then one task at same time
Q1) Is it correct definition for multitasking?

If we have two task running at same time, both task can not be executed at same time so one of them will be delayed , one task will be wait another task will be execute
Q2) one task will be wait another task will be execute but what decide that which one will be execute first and which one will be wait?

check out this definition
kernel -kernel is part of operating system that provide basic service to application software running on processor

multitasking - multitasking is process where one or more task run at same time on same single processor

scheduling- scheduling is process by which operating system decide which one task will be perform first on processor

please correct me If I am wrong

that looks correct

type of scheduling in real time operating system

First come First serve - task are executed on first come first serve basis
shortest Job first - task execute first which take minimum time to execute
priority based - each task has priority , higher priority task will be executed first

vead said:

type of scheduling in real time operating system

First come First serve - task are executed on first come first serve basis
shortest Job first - task execute first which take minimum time to execute
priority based - each task has priority , higher priority task will be executed first

Click to expand...

But none of these schemes is really RTOS - in fact I don't think there's really any such thing (not by my definition of 'real time').

throbscottle said:

Re ATM's - I am told they all run XP. Now that's scary...

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Anyway...as we all know M$ decided to end support for XP....
Sitting and looking the other night..lo and behold...updates still...

Suddenly the latest and greatest update for IE is available for XP too.....

Personally, I think M$ is absolutely shitting itself....XP is still everywhere......

I think they do not know what to do. I am so happy I am not in that BoardRoom right now

Cull XP completely..........NO NO NO say Millions of users Worldwide.

I love this as I still type from my Acer on XP.

Regards,
tvtech

throbscottle said:

Re ATM's - I am told they all run XP. Now that's scary...

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Not many would be running normal XP, they are far more likely to run XP embedded or Embedded Std 2009, both of which are still supported for a while yet.

And even if they weren't, most ATMs are relatively low risk. They are on a very secure, isolated and closely monitored network, the USB ports are inside a locked steel box, they only run a handful of custom written programs. There just aren't that many attack vectors.

POS terminals are a far higher risk. They often run desktop OS's, aren't frequently upgraded, are a connected to the internet, have keyboards & mice attached, aren't well secured physically, aren't locked down to prevent running additional software, have access to card details and can probably be used to launch an attack on the backend server which handles actual banking, etc.

tvtech said:

Personally, I think M$ is absolutely shitting itself....XP is still everywhere......

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I disagree, people still running XP don't hurt their bottom line. Big businesses running XP will either pay for extended support, or run an unsupported version (which means MS support costs go down). And in a lot of cases, they are probably getting their XP licenses as down level licensing from Win 7 or 8, so they are paying for the new OS even if they aren't using it.

Home users that continue to run XP wouldn't be a source of additional income even if XP continued to be supported.

I have exam question (RTOS subject )
define following
1. I/O subsystem
2.memory management
3)file system organizations

what does it mean by I/O subsystem
does It means Input output device for rtos

what does it mean by memory management
does it mean memory that use in rtos system

what does it mean '' file system ''
does it mean files that is used to store record example audio file, video file, Image file

please someone help me little bit

Presumably if it is in an exam, it is also in your text book. Those are fairly simple questions and while I'm sure that telling you the answers would help you pass the exam, I don't think it would help you in the long term.

I would suggest that you read your text book and lecture notes, and post back specific questions if you get stuck rather than just asking people to do your homework for you.

1. I/O subsystem
2.memory management
3)file system organizations

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Unfortunately, I know too much and it may not be what you studied.

1. I/O means a lot. Input/Output or how system communicates. Ports, memory, USB, etc. all all parts of the I/O subsystem. So are interrupts.

2, Memory management. You can write a book about this. I and D space protections are vital for a RTOS and just about any RTOS. Lots of stuff can go here.

3. File systems: Again another book. USB drives. SD cards. Think NTFS, EXT4 etc.
In a real simple case, like the original days where you had <100 MB drives you needed:
1) A bad block bit map
2) A used cluster bitmap
3) A directory structure. I did a lecture on an early file system before the PC.
4) A mount bit

A mechanism that verifies all of the files and directories when there is a power failure.

New drives have S.M.A.R.T data. Initially the bad sectors are mapped during manufacturer so some stuff is transparent.

Rule: Spit out what the teacher told you unless you can back up your response. I challenged plenty of questions and won with teach's response of "your not supposed to know that yet". Your not in that position.

KeepItSimpleStupid said:

Unfortunately, I know too much and it may not be what you studied.

1. I/O means a lot. Input/Output or how system communicates. Ports, memory, USB, etc. all all parts of the I/O subsystem. So are interrupts.

2, Memory management. You can write a book about this. I and D space protections are vital for a RTOS and just about any RTOS. Lots of stuff can go here.

3. File systems: Again another book. USB drives. SD cards. Think NTFS, EXT4 etc.
In a real simple case, like the original days where you had <100 MB drives you needed:
1) A bad block bit map
2) A used cluster bitmap
3) A directory structure. I did a lecture on an early file system before the PC.
4) A mount bit

A mechanism that verifies all of the files and directories when there is a power failure.

New drives have S.M.A.R.T data. Initially the bad sectors are mapped during manufacturer so some stuff is transparent.

Rule: Spit out what the teacher told you unless you can back up your response. I challenged plenty of questions and won with teach's response of "your not supposed to know that yet". Your not in that position.

Click to expand...

unfortunately I am doing part time course I don't have teacher
I know I have read to lot but I need t write within 4 page