Operating System is a system software that acts as a bridge between User and Hardware device to increase user activity by expanding User Interaction in more Simpler and effective manner.
Types of Operating System:
The operating system is classified into different types based on the following factors:
- Types of Operating System with respect to Number of users.
- Types of Operating System with respect to Processing method.
Types of Operating System with respect to the number of users:
Operating System is further classified into following types with respect to Number of Users. The further classified Operating System are:
a) Single user Operating System:
The type of O.S that supports only a single user at a time is called a single user operating system. This type of O.S can have only a single user at any given time. The single user O.S can’t handle multiple users at a time.
These O.S runs on microcomputer and example of single user O.S are MS Windows, Macintosh, DOS (Disk Operating System).
b) Multi-user Operating System:
The type of O.S that supports multiple (more than one) users at a time is called a multi-user operating system. This type of O.S can have more than one users at any given time.
These O.S allows more than one users to access a computer system at a time and examples of multi-user O.S are: MS Windows server, Unix, Linux.
Types of Operating System with respect to Processing method:
Operating Sytem is further classified into following types with respect to Processing Method. The further classified Operating System are:
a) Batch Processing Operating System:
The type of O.S which collects jobs (tasks) into batches (groups) before being processed by CPU is called batch processing O.S.
Batch Processing O.S, assigns the CPU to the jobs one by one when all the jobs are stored in a queue and a single job is processed at a time. Thus these O.S are slow in working.
b) Multiprogramming Operating System:
The type of O.S which loads multiple (more than one) programs into memory and executes them one by one by very quickly switching among them, is called multiprogramming O.S.
Multi Programming O.S, runs more than one programs at a time. In multi-programming O.S the operating system loads more than one programs into memory. The CPU processes these programs one by one by quickly switching among these programs.
In Multi Programming O.S there is quick switching of CPU among the programs, creates the illusion of parallel execution. In multi-programming, more than one programs become active in memory. Thus multi-programming makes efficient use of CPU time and memory.
c) Multi-Tasking Operating System:
The type of O.S which loads multiple (more than one) tasks of different programs into memory and executes them one by one by very quickly switching among them, is called multi-tasking O.S. This type of O.S, runs more than one tasks at a time. The term task refers to the part of a program, not the whole program itself.
The idea of multi-programming and multi-tasking is the same that is loading more than one program/tasks into memory and execute them one by one by a single processor. But the main difference is that in multi-programming the whole programs are loaded into memory while in multi-tasking, these programs are divided into parts, known as a task, and then from each the program, instead of the whole program the specific task that is need to be run first is loaded into memory. In this way, the O.S runs a program that is not completely loaded into memory.
Thus the idea of multi-tasking makes a very efficient use of main memory (RAM). The CPU switches among tasks very fast, and this creates the illusion of parallel execution of tasks.
d) Time-Sharing Operating System:
The type of O.S which slice processor (CPU) time into small fixed time slices and assign the processes (programs/tasks) to the CPU for that time slice is called time sharing O.S. If the allotted time slice (small fixed amount of CPU time) is expired the CPU is switched to next process (task/program).
The time sharing operating system gives equal opportunity to processes (programs/tasks) for processing. The CPU time is divided into a fixed small piece called time slice or quantum.
In time-sharing OS, a process is executed for that time slice (or quantum). On the expiry of this time slice, the CPU leaves the process (program/task) and move to some other process in memory. This technique of sharing CPU time is termed as time sharing.
Difference between Time sharing and Multi-tasking O.S:
The idea of time sharing and multi-tasking is the same, that is having more than one processes / tasks in memory and execute them one by one on a single processor. But the difference is that in a time sharing the CPU switches to some other process (task/program) in memory on the expiry of time slice. While in multi-tasking the CPU switches to some other task in memory, if the running task need some I/O (Input/Output) operation.
e) Real Time O.S:
The type of O.S which gives a quick response to users requests without delaying them are called Real time O.S. The real time O.S produces very quick result without wasting a time.
Real time O.S are very fast and quick respondent systems. These systems are used in an environment where a large number of events must be accepted and processed in a short time.
Real-time O.S are very powerful operating systems. The success rate of these operating systems is not only measured in term of the correctness of the computed result but also on the basis of the time at which the results are produced.
Advantages of Real Time Operating System:
- Guarantees a solution to the problem within a specific time.
- These are the multi-tasking operating system.
- These O.S responds very quickly to an event.
- When these O.S starts execution there processing can’t be interfered.
f) Multi-Processor Operating System:
The O.S which uses two or more processors (CPU’s) in a single computer system to process one or more programs / tasks is called multi-processor O.S. A multi-processor system can run multiple tasks in parallel on multiple CPU’s.
The multi-processor executes multiple tasks in parallel, therefore, a single program (process) is
divided into parts called thread and executed in parallel on multiple processors.
Advantages of Multi-Processing Operating System:
- Multiple programs can be run at a time
- If one processor fails, the processing load is shared by other processors.
Limitations of Multi-Processor OS:
- Cost and power consumption are the disadvantages of multiprocessor O.S.
- Large main memory is required.
- Handing more than one processes is difficult for the O.S.
g) Parallel processing Operating System:
In simple terms, Parallel processing is an approach where a single program is divided during execution in such a way that all the smaller parts can be processed independent of other parallel processing system multiple processes are executed in parallel on different proces (CPU’s).
The O.S. that is used to operate, control and manage a parallel processing system is called parallel processing O.S. Parallel processing is suitable for large and complex problems they require too much calculation simultaneously. Such a large problem is divided into smaller independent tasks and each task is executed by multiple processors concurrently.
h) Distributed Operating System:
A type of O.S that controls and runs distributed processing system is called distributed O.S. A distributed system is a set of computers that communicate and collaborate each other using software and hardware interconnecting components and makes them appear to the user as a single computer.
When independent computers are network together in such a way to work in a cooperative manner then they give raise to a distributed system. In the distributed system to perform a task, the computer communicates with each other and perform the operation in such a way that the do not feel that the computation is taking place on more than one machines.
Advantages of a distributed operating system:
- Sharing of resources.
- Reliability.
- Communication.
- Computation speedup.
Disadvantages of a distributed operating system:
- It needs network connectivity which is a difficult task.
- Security and privacy is an issue.
i) Embedded Operating System:
The type of O.S which are designed for a particular device is called Embedded O.S. This type of
O.S is used to run specific devices and can’t be installed on other devices instead of that for which it is designed.
These O.S are compact in size and efficient in performance. Embedded O.S are used in PDA’s,
electronic toys, digital cameras, Microwave ovens etc. Windows CE, Embedded Linux and Android are the examples of embedded O.S.
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