How does the OS handle the execution of multiple applications?

The OS manages the execution of multiple applications through a process known as multitasking.

Multitasking is a fundamental feature of modern operating systems, allowing multiple applications to run concurrently on a single computer. This is achieved through a combination of process scheduling, memory management, and virtualisation.

Process scheduling is the method by which the OS determines which processes, or applications, are given access to the system's resources at any given time. The OS uses a scheduler to allocate CPU time to each process, switching rapidly between them to give the illusion of simultaneous execution. This is known as time-sharing. The scheduler uses algorithms to decide the order of execution, taking into account factors such as priority, the need for specific resources, and the amount of CPU time the process has already received.

Memory management is another crucial aspect of multitasking. Each application requires a certain amount of memory to function, and the OS must ensure that each process has enough memory to run without interfering with the others. This is achieved through the use of virtual memory, where the OS uses a section of the hard drive as an extension of the computer's RAM. When an application is not in use, its data can be moved to this virtual memory, freeing up RAM for other processes.

Virtualisation is a technique used by the OS to isolate each application, giving it its own virtual machine that it believes it has exclusive control over. This prevents applications from interfering with each other and allows the OS to maintain control over system resources. Each virtual machine has its own virtual memory, CPU, and other resources, allowing the OS to manage each application independently.

In summary, the OS uses a combination of process scheduling, memory management, and virtualisation to manage the execution of multiple applications. This allows for efficient use of system resources and ensures that each application has the resources it needs to function correctly.