Kernal

The kernel is the essential center of a computer operating system, the core that provides basic services for all other parts of the operating system.As a basic component of an operating system, a kernel provides the lowest-level abstraction layer for the resources.

The kernel's primary purpose is to manage the computer's resources and allow other programs to run and use the resources like the CPU, memory and the I/O devices in the computer.

The facilities provides by the kernel are :

• Memory management
  The kernel has full access to the system's memory and must allow processes to access safely this memory as they require it.
• Device management
  To perform useful functions, processes need access to the peripherals connected to the computer, which are controlled by the kernel through device drivers
• System calls
  To actually perform useful work, a process must be able to access the services provided by the kernel.

Types of Kernel:

• Monolithic kernels
  Every part which is to be accessed by most programs which cannot be put in a library is in the kernel space:
  Device drivers
  Scheduler
  Memory handling
  File systems
  Network stacks
• Microkernls
  In Microkernels, parts which really require to be in a privileged mode are in kernel space:
  -Inter-Process Communication,
  -Basic scheduling
  -Basic memory handling
  -Basic I/O primitives