What are system calls, and why arethey essential for user-level programs to interact with the kernel in an operating system?A system call is like a special key that allows regular programs (in user mode) to briefly switch to a more powerful mode (kernel mode) when they need to do something important, like accessing hardware or managing system resources. It's like getting permission from the boss (kernel) to use the computer's superpowers for a specific task. Once the task is done, the program goes back to its regular user mode, like exiting the boss's office and returning to its normal work. This controlled transition between modes ensures the computer's security and stability