What does "context switch" allow an operating system to do?

A context switch is a crucial mechanism in operating systems that facilitates multitasking by allowing the system to switch from one process to another. This process involves saving the state of the currently running process so that it can be resumed later, and then loading the state of the new process that is to be executed.

When a context switch occurs, the current state of the CPU registers, program counter, and other critical process-specific information is stored in the process control block (PCB) of the current process. This ensures that when the operating system schedules this process to run again, it can restore its state exactly as it was left. Then, the OS loads the PCB of the next process into the CPU and begins or resumes its execution. This switching allows multiple processes to share the CPU in a way that they appear to run simultaneously, even though, in reality, they are allocated time slices in rapid succession.

The other options, while related to operating system functionality, do not accurately describe the primary purpose of context switching. Running multiple applications, memory allocation for processes, and file synchronization involve different mechanisms and operations within the operating system that are not directly about the context switch itself.