Batch, multi programming. Multitasking, time sharing, parallel, distributed & real -time O.S.
Types of Operating SystemsEdit
Q. Explain different types of operating systems ?
Ans:- There are various types of operating systems. Some of them are mentioned below :-
a) Batch OS
b) Multiprogramming OS
c) Time Sharing OS
d) Multitasking OS
e) Distributed OS
f) Parallel OS
g) Real Time OS
a) Batch OS :-Edit
Batch processing requires grouping of similar jobs which consist of programs and data. Batch processing is suitable for program with large computation time with no need for user interaction. Initially serial system was used where execution of program is sequential, but it was very slow.
Computer operator gives a command to start the processing of a batch, the kernel set up the processing of the first job. Job was selected from the job queue and loaded into main memory when a job completed execution its memory was released and the output for the job was copied .When a job is completed it returns control, which immediately reads in the next job. Following figure shows concept of batch system. Scheduling is also simple in batch system
i.e. FCFS ( First Come First Serve )
Advantages of batch system :- Increased performance as job switching takes place very fast.
Disadvantage of batch system :- 1)Turn around time can be very large. 2) Program debugging is difficult.
b) Multiprogramming OS :-Edit
CPU remains idle in batch system. At any time either CPU or I/O device was idle in batch system to kee CPU busy, more than one program job must be loaded for execution. It increases the CPU utilization. OS executes multiple programs. One program gives control to other program when it is waiting for some I/O or when it completes its execution. Here CPU Scheduling is required. Memory management is also required.
c) Multitasking OS :-Edit
Multitasking means that the computer can deal with more than one program at a time. Here CPU scheduling must be given. Here every process is having its PCB (Process Control Block ). Which stores all registers, memory, etc. When one program gives control of CPU to other program before its execution, it is called as context switching.
d) Time Sharing OS :-Edit
In case of multiprogramming only one program runs at a time, that program gives control to other program when it will complete its tasks. It means if we have more processes then last process has to wait for very long time. To avoid this time sharing OS is used where certain time slot is allocated to every program. It will get CPU only its given time slot. After that CPU will be hand over to other program. Here most of the time round robin scheduling is used. It is more complex than time sharing OS.
e) Distributed OS :-Edit
A Distributed operating system is one that look to its users like an ordinary centralized operating system but runs on multiple independent CPU. User sees the environment as a virtual environment . Here client-server mechanism is used. User request OS service to server. Server gives response to that request. Distributed OS allows programs to run on several processors at the same time without users being aware of this distribution. Distributed systems are more reliable than uniprocessor based systems. The distributed system have a performance advantages over traditional centralized systems. It is simple to implement. But that is also disadvantage for distributed systems.
f) Parallel Computing :-Edit
The use of multiple computers with multiple processes to solve a problem with greater speed than using a single computer.
A parallel computer is a collection of processing elements that cooperate to solve large problem fast. Parallel computing is dividing up tasks ver multiple microprocessors which are independent of each other. Instructions from each part execute simultaneously on different CPU.
g) Real Time OS :-Edit
Time constraints is the key parameter in real time operating system. It is used in air traffic control, satellite, etc. Real time system. Are of two types. Hard real time and soft real time critical task is completed within the time limit in hard real time system. Soft real time cannot guarantee that it will be able to meet deadline under all condition.
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