LINUX is
type of Operating system that controls your Computer. LINUX is one of the most
popular version of operating System. It is similar as UNIX.
Architecture of Linux consists of 5 parts.
1.User Application
2. GNU C Library
3.System Call
4. Kernel
5. Hardware/Controller or Platform
These 5 parts are divided into two other parts
in LINUX Architecture. One is known as
User Space and the other is Kernel Space. User Space is the Space in memory
where user processes run. This space is above the Kernel. And this is
protected. Kernel Space is the Space in memory where all kernel Services are
provided kernel processes. A user has access to it only through the system
call. A user process becomes a kernel process ,when it executes a system call.
When system call is executed the arguments to the call are passed from user
space to kernel space. User Application and GNU C library come into User Space.
And System Call interface, kernel, kernel code come in kernel space. Whole is
called Linux. At the top is user applications. User Applications are the
commands used by operating system. User Applications are executed in user
space. User Applications directly access
the GNU C library Commands. There is also a GNU C library which provides
system Call interface. The system calls is the separation of kernel space from
user space. Every operating system has many system calls. Then this system call
interface connects to kernel. A kernel is really nothing more than a resource
manager. Whether the resource being managed is a process, memory, or hardware
device, the kernel manages and access to the resource between multiple
competing users(both in the kernel and in user space). The kernel is like a
server that response to the hardware interrupt requests and system calls. This
Kernel provides procedure between User Space and Kernel Space. Kernel and User applications occupies address spaces.
The kernel occupies single address space. This kernel can be divided into two
levels. The first level is system call interface that implements the basic
function like read and write. The second is kernel code. This code is common
for every operating system whose supported by Linux.
Linux System Architecture Also consists of following
layers:
Hardware layer: Hardware layer consists of all
peripheral devices like RAM, HDD, CPU.
..
Kernel:
Core component of Operating System, interacts directly with hardware, provides
low level services to upper layer components. The Linux kernel includes device
driver support for a large number of PC hardware devices (graphics cards,
network cards, hard disks etc.), advanced processor and memory management
features, and support for many different types of file systems. In the terms of
the services, it provides to application programs and system utilities.
Shell:
An interface to kernel, hiding complexity of kernel's functions from users.
Takes commands from user and executes kernel's functions. A shell is the
interface between the user, applications, utilities and the kernel of the
operating system. The shell accepts and interprets commands, and forwards them
to the kernel. Commands can be entered either from a command prompt or a
script. Without a shell we can’t interface with the rest of the operating
system. A Linux shell is comparable to the DOS in Windows.
Utilities:
Utility programs giving user most of the functionalities of an operating
systems. To form an operating system, we need tools and utilities. Utilities
are used to manage the system and applications are programs like word
processing.
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