Unix operating system is breifly discussed including the process management, memory management anf file management in UNIX OS.

1. Unix Operating
System

2. • Unix is a
Multi-tasking
Multi-user operating system.
• Many users can be logged into a system simultaneously, each running
many programs.
• The kernel job is to
Separate each process and user
Regulate access to system hardware i.e. memory & I/O devices.

3. History
• First version was created in Bell labs in 1969
• By KenThompson, Denis Ritchie, Brian Kernighan & Joe Ossanna
• Implemented on PDP-7
• It was given the name UNIX by Brian Kernighan
• 1973 unix was rewritten in C language
• 1980 BSD 4.1 (Berkeley Software Development)
• 1988 AT&T and Sun Microsystems jointly develop SystemV Release 4
(SVR4).This later developed into UnixWare and Solaris 2
• 1991 Linux was originated.

4. Structure of UNIX

5. UNIX Architecture
• Kernel:The kernel is the heart of the operating system. It interacts
with hardware and most of the tasks .
• Shell:The shell is the utility that processes your requests.When you
type in a command at your terminal, the shell interprets the
command and calls the program that you want
• Commands and Utilities: There are various command and utilities
which you would use in your day to day activities. cp, mv, cat and
grep.
• Files and Directories: All data in UNIX is organized into files. All files
are organized into directories.These directories are organized into a
tree-like structure called the file system. .

6. HARDWARE REQUIREMENT
• RAM – 256 MB .
• HARD DRIVE – 10 minimum and maximum depends on the user
requirement.
• VIDEO– Minimum 800X600.
• MOUSE – Any.
• REMOVAL MEDIA – Most SCSI.
• PRINTER – Almost any parallel or serial port.
• MODEM– Most serial
• NIC – 3Com, Novell, HP, Intel - Clones are NOT recommended.

7. FEATURES
• Multi-user system : Multi-user capability of UNIX allows several users
to use the same computer to perform their tasks.
• Multi-tasking : Multitasking is the capability of the operating system
to perform various task simultaneously, i.e. a user can run multiple
tasks concurrently.
• Programming Facility : UNIX is highly programmable, the UNIX shell
has all the necessary ingredients like conditional and control
structures, etc.

8. CONT…..
• Security : UNIX allows sharing of data; every user must have a single
login name and password. So, accessing another user’s data is
impossible without his permission.
• Portability : UNIX is portable because it is written in a high level
language. So , UNIX can be run on different computers.

9. INTERFFACES OF UNIX
Graphical User Interfaces (GUIs)
• When you logon locally, you are presented with graphical
environment.
Command Line Interface
• You also have access to some UNIX servers as well.
• You can logon from virtually any computer that has internet access
whether it isWindows, Mac, or UNIX itself.

10. Unix
Process Management

11. Process
• A program that is claimed to be executing is called a process.
• For a multitasking system, a process has at least the following three
states:
1.Ready state
2.Running state
3.Sleeping state

12. Process Management
• Multi-tasking system
• Multiple programs can be executed simultaneously
• 3 types of processes are available
System processes (Execute OS code)
User processes (Execute user program code)
Daemons process

13. Process Management
• Processes will alternatively get into the CPU one after the other
(called the round robin scheme).
• At the time that a process is selected to be “in” the CPU
It goes from ready state to running state
• After that, it will be swapped out
It goes from running state back to ready state
• Or it may due to the waiting of an I/O device, e.g. mouse
It goes from running state to sleeping state
• When obtaining the required resource
It goes from sleeping state to ready state

14. MEMORY MANGMENT SYSTEM
• Primary memory is a precious resource that frequently cannot
contain all active processes in the system.
• The memory management system decides which processes should
reside in memory.
• It monitors the amount of available
memory.

15. UNIX Memory Management Policies
• Swapping
– Easy to implement
– Less system overhead
• Demand Paging
– Greater flexibility

16. Swapping
• The swap device is a block device in a configurable section of a disk
• • Kernel allocates contiguous space on the swap device without
fragmentation
• It maintains free space of the swap device in an in-core table, called
map
• The kernel treats each unit of the swap map as group of disk blocks
• As kernel allocates and frees resources, it updates the map
accordingly

17. Demand Paging
• Not all page of process resides in memory Locality
• When a process accesses a page that is not part of its working set, it
incurs a page fault.
• The kernel suspends the execution of the process until it reads the
page into memory and makes it accessible to the process

18. FILE MANAGEMENT SYSTEM
Types of files in UNIX
• Ordinary Files: A file on the system that contains data, text, or
program instructions.
• Special Files: Some special files provide access to hardware such as
hard drives, CD-ROM drives, modems, and Ethernet adapters.
• Directories: Directories store both special and ordinary files. For
users familiar with Windows or Mac OS, UNIX directories are
equivalent to folders.

19. CONT…
• FILES AND DIRECTORY ACCESS MODES
• Read
• Write
• Execute

20. ADVANTAGES
• Full multitasking with
protected memory.
• Multiple users can run multiple
programs each at the same
time..
• Portable.
• Machine independent.
• Efficient virtual memory.
• Access Control and security.
DISADVANTAGES
• Its command line shell interface
is not user-friendly.
• It has a lot of utilities(over 400
standard ones)
• To use UNIX well, the user
needs to understand some of
the main design features.

21. Conclusion
• Better multiuser approach.
• Better process hierarchy.
• Use of daemons.
• Better programming
environment.
• Cost
• User
• Processors
• Security
• Multiprocessing
• Open source
• File system supported
So we can say UNIX is far more better than WINDOWS .