Features of UNIX:Portability,Multiusers,security,multitasking

1. UNIX
AN INTRODUCTION
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2. • In 1965 Bell Laboratories ,general Electrical company and
Massachusetts Institute of Technology developed an
operating system called MULTICS.
• MULTICS was named as UNIX in1969.
• In 1971 Unix was ported to PDP-11 computers.
• But this version was not portable for new machines.
• To resolve this problem Ken Thompson created a new high
level language called “B” and rewritten the whole UNIX
code in this high level language.
• Dennis Ritchie modified it to a new high level language
called “C”.
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HISTORY

3. Features of UNIX
Multi-user OS:
• Multi –user means more than one user.
• Terminals have monitors and keyboards that are connected to
main computer .
• A user is allowed to sit on different terminals and access the
main computer and its resources by giving his login name
and password.
• These terminals that are connected to the main computer are
called Dump terminals.
• They can never act as independent machines and are fully
dependent on main computer.
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4. • Multitasking
Capacity of an OS to perform multiple task
simultaneously.
It uses Time sharing techniques.
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5. • Portability
Ability to adapt to different computers
• Security
To prevent unauthorized access.
Password to individual user:
The system will log on for a particular user
after verifying his user name and password.
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6. File access security:
At file level there are Read ,Write and eXcute
permissions for each file .
File Encryption and decryption:
Unreadable format
Communication:
Exchange data through network among its users.
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7. Unix System Organisation
• Utilities and Applications:
Represents user programs and commands.
• Shell
Command interpreter
Interprets the user commands and conveys
them to the kernel that executes them.
Mediator between user and kernel.
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8. • Types of shells
Commonly used shells are
1)Bourne shell :
Default shell.
The prompt of this shell is dollar ($).
2)C shell:
The prompt of this shell is %.
3)Korn shell:
The prompt of this shell is dollar ($).
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9. • Kernel
 Heart of the Unix System.
 Loaded into the memory whenever the system is
booted.
 It manages resources such a files, memory, I/O etc
and also keeps track on program execution.
 It doesnot interact with the user directly .
 Shell is used as a mediator b/w user and kernel.
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10. THANK YOU
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