over view of unix os

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Unix Structure Organization
Name: Alagiya Kishan V.
Class :Tybca Div : 1
Roll no : 1

2. 01/07/16 created by kishan alagiya 2
Introduction
 UNIX is a layered operating system .
 Developed year : 1969
 Place : AT&T Bell Labs
 Developer Include: Ken Thompson, Dennis
Ritchie, Douglas McIlroy, and Joe Ossanna.
 Other : Solaris Unix, AIX, HP Unix, BSD

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 There are three major components of UNIX operating
system.
1)Shell
2)Kernel
3)Hardware
 The function of UNIX operating system is managed in
three levels. That show in figure

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user

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Hardware
 The innermost layer is hardware.
 That provides the services for the
operating system.

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Shell
 Command interpreter
 Then shell conveys interpreted command to the
kernel which ultimately executes them.
 When any user logged in successfully to the UNIX
system then a shell is allocated to that user
 Shell offers a prompt through which user issue a
command to the UNIX system.

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Kernel
 Kernel is an important component of UNIX OS. It
resides between hardware and shell.
 Kernel is a heart of UNIX, which interacts with the
actual hardware in machine language.
 The kernel has overall control of everything.
 The kernel performs various function such as:

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 It manages files, carries out all the data transfer
between the file system and the hardware.
 It manages memory i.e. assigns memory to
each of the programs that are running.
 The kernel is responsible for scheduling of
various programs running in memory or
allocation CPU time to all programs.
 It also handles any interrupts issued, all I/O
operations, and all other low-level services and
so on.

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 The kernel program is usually stored in a
file called ‘UNIX’ whereas the shell
program is in a file called ‘sh’.
 There may be several shells running in
memory but only one kernel.
 In that only one program will execute all
other are waiting for it turns.
 So kernel is sufficient to execute a
program.

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Utilities
 Utilities are a standard UNIX programs that
perform system function.
 Utility can also refer to as a command that is used
to do work such as mv, mkdir…
 mv : is uses to move file or directories. Text
editor, search program, sort program etc. are
examples of UNIX utilities.

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 In that some of the utilities are complicated
application.
 For example, the UNIX emails system, text
editors such as VI, emacs and Pico.
 All these utilities are large systems in
themselves.
 Other utilities are short and simple function such
as the list (ls), cat, and clear so on.

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Application
 The program written by system
administrator, professional programmers,
or users are known as application
Example: our os , vlc , putty , firefox
 Applications are not a standard part of
UNIX system.
 They provide an extended capability to
the system.

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Thank you