Typically, there are three situations that a context switch is necessary, as shown below. on behalf of the operating system, it’s not safe for user programs to be able to service or ignore interrupts, nor is it safe for them to have raw access to devices. It is one of the essential features of the multitasking operating system. A typical process context switch happens like this: Process context switches are initiated by a thread-context switch, so all of the above, 1-9, is going to need to happen. The time involved in the context switching of one process by other is called the Context Switching Time. That's it for this blog. Here, the context switching is so fast that the user feels that the CPU is executing more than one task at the same time. The processes are switched so fastly that it gives an illusion to the user that all the processes are being executed at the same time. Now, you have to move the PCB1 to the relevant queue i.e. Multitasking gives an illusion to the users that more than one process are being executed at the same time. The disadvantage of context switching is that it requires some time for context switching i.e. The kernel must save the context of the previous process in its Process Control Block and then must load the saved context of the new process which is scheduled to run. Save the context of the process that is currently running on the CPU. Describe the actions taken by a kernel to context-switch between processes. Time is required to save the context of one process that is in the running state and then getting the context of another process that is about to come in the running state. The following diagram depicts the process of context switching between the two processes P1 and P2. When a process of high priority comes in the ready state. But the context switching process involved a number of steps that need to be followed. At step 5 above, the scheduler decides to run a thread belonging to a different process from the one that owned the previously-running thread. You can't directly switch a process from the running state to the ready state. A context is the contents of a CPU's registers and program counter at any point in time. A context switch occurs when a computer’s CPU switches from one process or thread to a different process or thread. multiprogramming with time-sharing(learn more about multitasking from here). The time involved in the context switching of one process by other is called the Context Switching Time. Any operating system that allows for multitasking relies heavily on the use of context switching to allow different processes to run at the same time . Context Switch in Operating System Processes, Any operating system that allows for multitasking relies heavily on the use of context switching to. Select a new process for execution. PCB1. In response to a clock interrupt, the OS saves the PC and user stack pointer A context switching is a process that involves switching of the CPU from one process or task to another. 2. Update the process control block of the selected process. Interrupt causes the operating system to change a CPU from its current task and to run a kernel routine. This may be required, depending on how address translation is managed. Context switching can happen due to the following reasons: The process of context switching involves a number of steps. When a transition between the user mode and kernel mode is required then you have to perform the context switching. Switching the CPU to another process required performing a state save of the current process and state restore of different process and this task is known as context switching. Similarly, if you want to execute the process P1 again, then you have to follow the same steps as mentioned above(from step 1 to 4). You have to save the context of that process.

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