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#OS #operatingsystem #Multiprogramming #Batchoperating #Multiprocessing #TimesharingOS #VirtualMachine

Lecture-2

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#Virtual Machine
#Batch Operating System
#Multiprogramming OS
#Multitasking / Time Sharing / Fair sharing OS
#Multiprocessing OS
#Real Time OS

Virtual machines:
Virtual machine is concept, which describe that all process or programs currently running in the system will be supported with a copy.
So the user of the process will get the impression as if he is the sole owner of the OS resources.
In fact scheduling mechanism will support the process with necessary resources.

Batch-operating OS: Early computers were enormous large machines run from a console.
The operating system in these early computer was fairly simple.
Its major task was to transfer control automatically from one job to another.
A simple batch operating system thus normally reads a stream of separate jobs, each with its own control cards that predefine what the job does.
When the job is complete, its output is usually printed.
The definitive feature of a batch system is the lack of interaction between the user and the job while that job is executing.




Multiprogramming OS:
A mode of an operation that provide for the interleaved execution of two or more computer programs by a single processor.
Multiprogramming is accomplished by the CPU temporarily suspending execution of it’s current program, beginning execution of a second program & returning to the first program later.





Time-sharing OS:A time sharing operating system allow many users to share the computer simultaneously. Since each action or command in a shared system tends to be short, only a little CPU time is needed for each user. A time operating system users CPU scheduling of multiprogramming to provide each user with a small portion of a time-shared computer. Time-shared operating system are even more complex than multiprogramming operating system.
Time-sharing systems provide file system. It also provides a mechanism for concurrent execution, which requires sophisticated CPU-scheduling schemes.