Learning About Time Sharing Operating System

Time sharing operating system can execute multiple processes at the same time. They leverage CPU and reduce its idle time. Several users can use a single computer simultaneously in case of time sharing.

In this article, we will discuss the time sharing operating system, its working, advantages, and disadvantages. 

Table of Contents

• What is a time-sharing operating system?
• Techniques used for time sharing
• Working
• Advantages
• Disadvantages

What is a time sharing operating system?

Time sharing operating system is a type of operating system. It uses CPU scheduling and multiprogramming for every user, along with a small part of the shared computer at once. The concept of time-sharing is beneficial. It allows multiple people at different locations to use one particular computer system simultaneously. Here, the processor’s time is shared among multiple users at the same time. It is a logical extension of multiprogramming and is often referred to as multitasking. 

In data processing, it is the method of operation where multiple users having different programs interact simultaneously with CPU. A CPU operates faster; it can solve discrete problems during input and output processes in sufficient time. Since switching between tasks is very fast, it almost feels that every task is running simultaneously. 

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Techniques Used For Time Sharing

Let us discuss the following techniques that are commonly used in time-sharing systems.

1. CPU scheduling 

It is a process that allows a process to use the CPU while delaying another process, thus allowing full use of the CPU. Through CPU scheduling, the system becomes faster and more efficient. During the CPU idle time, the operating system selects one of the processes in line using the temporary scheduler. This scheduler selects between memory processes that are ready to launch and assigns CPU to one of these processes. 

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2. Multitasking

In an operating system, it refers to allowing a user to perform multiple tasks simultaneously. In this case, time sharing operating system tracks where exactly you are in a task. It also monitors how you swap from one to another without losing any information. In such an environment, every resource of the computer is allocated to different applications. 

These are managed in a way that each one gets a share of resources based on priority. In case the CPU resources are not available, the operating system schedules different active processes. This is done by performing process switch at regular time intervals. Through this, it distributes available CPU cycles as per well defined priority policy.

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3. Multi Programming 

When a program waits for the input/output transfer in a multi-programming system, other processes are ready to use the CPU. Several jobs share CPU time while multiprogramming. The aim of multi programming is to manage every resource of the system. 

In such systems, multiple users can accomplish their tasks simultaneously. All jobs will not be run simultaneously, but several jobs will be run on the processor at the same time. The parts of other processes are executed first, followed by other parts.

4. Parallel systems

These speed up the execution of the program. The program is divided into multiple fragments, and these fragments are processed at the same time. It simultaneously uses multiple computer resources. Due to this, tasks are performed much faster. 

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How does Time Sharing Operating Systems Work?

Let us now understand how time sharing operating systems work. For each process, a short duration of time, around 10-100 milliseconds, is allotted. This is known as time slot/slice or quantum. Here, every process has a fixed time slice. There are following three states for processes:

1. Active state: This is the state of that process that is currently being processed by the CPU.
2. Ready state: This is the state of the next process to be executed. It means the process is ready for execution and will be taken over by the CPU once the process in active state is executed. There can be multiple processes in a ready state.
3. Waiting state: This is the state of a process that is neither in active nor ready state. This is the state where the process is waiting for an I/0 process to be completed. 

Consider an example to understand the working. Suppose there are three processes running on a system. In a time-sharing operating system, for each process, a time slot of 5 nanoseconds is allocated. Once a process is executed and completed, the next process will be executed for the next 5 nanoseconds. Similarly, when this task is completed, the third process will be executed for the next 5 nanoseconds. This process will continue till every process is completed. 

Advantages of Time Sharing Operating Systems

The following are the advantages of a time sharing operating system:

• Every user gets dedicated time for every operation.
• Multiple users can work simultaneously o the same computer.
• The waiting period is very less for every task to end.
• Processing is very quick for multiple tasks.
• CPU usage reduces its idle time.

Disadvantages of Time Sharing Operating Systems

While time sharing operating systems have several advantages, there are some drawbacks as well:

• Resource consumption in time sharing systems is more due to which special operating systems are required.
• These systems require software with higher specifications.
• Such systems may face issues related to the security and integrity of user data and programs.
• The system may slow down or hang since several users and applications use the system.

Conclusion

Hope this article has been able to explain to you about time sharing systems. Since in such systems, multiple jobs are kept in the memory, these should have memory management and security. For achieving a good response time, jobs might have to be swapped in and out from the main memory.