What is RTOS? (Question 18 in OS)

README.md

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 16.[Write top 10 examples of OS?](./operatingSystem.md/Ques16.md)
 
+17.[What is spooling?](./operatingSystem.md/Ques17.md)
+
+18.[What do you mean by RTOS?](./operatingSystem.md/Ques18.md)
+
 ### Software Engineering
 
 1.[What are bitmap images?](./softwareEngineering.md/ques1.md#What-are-bitmap-images)

operatingSystem.md/Ques17.md

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+**What is spooling ?**
+
+SPOOL is an acronym for simultaneous peripheral operations online. Spooling is a process in which data is temporarily held to be used and executed by a device, program, or system.
+In spooling, there is no interaction between the I/O devices and the CPU. That means there is no need for the CPU to wait for the I/O operations to take place. Such operations take a long time to finish executing, so the CPU will not wait for them to finish.
+The biggest example of Spooling is printing. The documents which are to be printed are stored in the SPOOL and then added to the queue for printing. During this time, many processes can perform their operations and use the CPU without waiting while the printer executes the printing process on the documents one-by-one.

operatingSystem.md/Ques18.md

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+**What do you mean by RTOS?**
+Real Time Operating System (RTOS) is an operating system that is used for real-time applications i.e., for those applications where data processing should be done in a fixed and small measure of time. It performs much better on tasks that are needed to be executed within a short time. It also takes care of execution, monitoring, and all-controlling processes. It also occupies less memory and consumes fewer resources. 
+
+Types of RTOS:
+
+Hard Real-Time
+Firm Real-Time
+Soft Real-Time