Architecture of operating system on kernal level.

2. An operating system is a software that :
 acts as an interface between the user and the
computer hardware and controls the execution of all
kinds of programs.
 performs all the basic tasks like file management,
memory management, process management,
handling input and output, and controlling
peripheral devices such as disk drives and printers.
 Some popular Operating Systems are Linux,
Windows, OS X, VMS, OS/400, AIX, z/OS, etc.

4. 1) Monolithic Operating System
2) Layered Operating System
3) Microkernel Operating system
4) Networked and Distributed Operating System

5.  A monolithic os is an operating system
architecture where the entire operating system is
working in kernel space and is alone in supervisor
mode.
 Every component of the operating system is
contained in the kernel and can directly
communicate with any other (i.e., simply by using
function calls). The kernel typically executes with
unrestricted access to the computer system.
 Ex:- OS/360,VMS and LINUX.

7.  As operating systems became larger and more
complex, purely monolithic designs became unwieldy.
The layered approach to operating systems attempts
to address this issue by grouping components that
perform similar functions into layers.
 Each layer communicates exclusively with those
immediately above and below it.
 Lowerlevel layers provide services to higher-level ones
using an interface that hides their implementation.
 EX :- The THE operating system is an early example of
a layered operating system .Windows XP and Linux,
implement some level of layering.

9.  In microkernel designs, most operating system
components—such as process management,
networking, file system interaction and device
management—execute outside the kernel with a lower
privilege level.
 Microkernels exhibit a high degree of modularity,
making them extensible, portable and scalable.
Further, because the microkernel does not rely on
each component to execute, one or more components
can fail, without causing the operating system to fail.
 EX :- Linux and Windows XP contain modular
components.

11.  A network operating system enables its processes to
access resources (e.g., files) that reside on other
independent computers on a network.
 The structure of many networked and distributed operating
systems is often based on the client/server model.
 The client computers in such a network request
resources—such as files and processor time—via the
appropriate network protocol. The servers respond with
the appropriate resources.
 A distributed operating system is a single operating
system that manages resources on more than one computer
system.
 EX :- MIT's Chord operating system and the Amoeba
operating system from the Vrije Universiteit (VU) in
Amsterdam.