How dose concurrent programming is done in operating system?
Concurrent processing is a computing model
in which multiple processors execute instructions simultaneously for better
performance. Concurrent means, which occurs when something else happens. The
tasks are broken into sub-types, which are then assigned to different
processors to perform simultaneously, sequentially instead, as they would have
to be performed by one processor. Concurrent processing is sometimes synonymous
with parallel processing.
The
term real and virtual concurrency in concurrent processing:
1.
Multiprogramming Environment :
In multiprogramming environment, there are multiple tasks shared by one
processor. while a virtual concert can be achieved by the operating system, if
the processor is allocated for each individual task, so that the virtual
concept is visible if each task has a dedicated processor. The multilayer
environment shown in figure.’
1. 2 .Multiprocessing Environment :
In multiprocessing environment two or more
processors are used with shared memory. Only one virtual address space is used,
which is common for all processors. All tasks reside in shared memory. In this
environment, concurrency is supported in the form of concurrently executing
processors. The tasks executed on different processors are performed with each
other through shared memory. The multiprocessing environment is shown in
figure.
3. Distributed Processing
Environment :
In a distributed processing environment, two or
more computers are connected to each other by a communication network or high
speed bus. There is no shared memory between the processors and each computer
has its own local memory. Hence a distributed application consisting of concurrent
tasks, which are distributed over network communication via messages. The
distributed processing environment is shown in figure.


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