From the beginning- Kernel

Many people have the misconception about "Linux" or "Hurd" are the names of operating systems. Currently only some technology geek and computer science know it the a kernel is only the heart of an operating system not the operating system its like your own heart you can't live without it but your heart alone cannot make you a human, you need bones and flesh to be a complete human, the same applies for operating systems also.

On the definition of 'kernel' Jochen Liedtke said that the word is "traditionally used to denote the part of the operating system that is mandatory and common to all other software."

The kernel's primary purpose is to manage the computer's resources and allow other programs to run and use these resources. Typically, the resources consist of:

• The Central Processing Unit (CPU, the processor). This is the most central part of a computer system, responsible for running or executing programs on it. The kernel takes responsibility for deciding at any time which of the many running programs should be allocated to the processor or processors (each of which can usually run only one program at a time)
• The computer's memory. Memory is used to store both program instructions and data. Typically, both need to be present in memory in order for a program to execute. Often multiple programs will want access to memory, frequently demanding more memory than the computer has available. The kernel is responsible for deciding which memory each process can use, and determining what to do when not enough is available.
• Any Input/Output (I/O) devices present in the computer, such as keyboard, mouse, disk drives, printers, displays, etc. The kernel allocates requests from applications to perform I/O to an appropriate device (or subsection of a device, in the case of files on a disk or windows on a display) and provides convenient methods for using the device (typically abstracted to the point where the application does not need to know implementation details of the device).

Key aspects necessary in resource managements are the definition of an execution domain (address space) and the protection mechanism used to mediate the accesses to the resources within a domain.

Kernels also usually provide methods for synchronisation and communication between processes (called inter-process communication or IPC).

A kernel may implement these features itself, or rely on some of the processes it runs to provide the facilities to other processes, although in this case it must provide some means of IPC to allow processes to access the facilities provided by each other.

Finally, a kernel must provide running programs with a method to make requests to access these facilities.