The document describes the structure and organization of the UNIX operating system. It discusses three major components: the shell, kernel, and hardware. The shell conveys commands from users to the kernel to execute. The kernel resides between the hardware and shell and manages processes, memory, I/O, and other low-level services. Utilities are standard programs that perform system functions like moving files, while applications provide extended capabilities and are created by users, administrators, and programmers rather than being part of the core UNIX system.

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

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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