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Transcript of UNIX
What is UNIX?
has traditionally been applied to the family of multitasking, multiuser computer operating systems that derive from the original AT&T UNIX operating system, developed in the 1970s at the Bell Labs research center by
Ken Thompson, Dennis Ritchie, and others
UNIX operating system
is a set of programs that act as a link between the computer and the user.
The History of UNIX
The Structure of UNIX
What is an Operating System?
The General Characteristics of UNIX
Multi-user and Multi-tasking
Over 30 Years Old
Large Number of Applications
Free Applications and Even a Free Operating System
Less Resource Intensive
Command Line Interface
Process Scheduling Queues
Types of Processes
Modes of Execution
Types of Processes
Execute OS code
Execute user program code
Operating system functions executes within user process
Ready to Run in Memory
Asleep in Memory
Ready to Run, Swapped
is a precious resource that frequently cannot contain all active processes in the system.
memory managment system
decides which processes should reside (at least partially) in main memory.
Easy to implement
Less system overhead
Basic Types of Files
File Access Modes
Starting a Process
Used to transfer from user mode to system mode
James Matthew Santonil
Jan Christian Fontillas
Arnold Bryan Raguin
Lanz Tedrick Micua
John Ian Lemuel Cabizo
Vincent Andrei Enriquez
John Michael Quines
Arnel Dela Pena
Joshua Cyril Ang
Paul Owen Aniano
first "UNIX" system
in the Bell AT&T laboratories at Murray Hill in New Jersey from 1965. His aim was to develop a simple interactive operating system, called
in order to run a game which he had created.
On April 1969, the AT&T laboratories decided to use the
(General Electric Comprehensive Operating System) instead of Multics. However,
who joined the team needed to make the spacetravel game work on a smaller machine, this is why they recreated the system in order to create a limited version of Multics called
(Uniplexed Information and Computing Service), quickly shortened to UNIX.
January 1st 1970 is considered as the birth date of UNIX system.
played a large part in the definition of the
, so the whole system was entirely rewritten in C in 1973 and called
Unix Time-Sharing System
(TSS). When the system passed version 7 in 1979, its development was accompanied by many notable modifications.
Commands and Utilities
Files and Directories
The kernel is the heart of the operating system. It interacts with hardware and most of the tasks like memory management, task scheduling and file management.
There are various command and utilities which you would use in your day to day activities. cp, mv, cat and grep etc. are few examples of commands and utilities. There are over 250 standard commands plus numerous others provided through 3rd party software. All the commands come along with various optional options.
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. The shell uses standard syntax for all commands. C Shell, Bourne Shell and Korn Shell are most famous shells which are available with most of the Unix variants.
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 filesystem.
operating system (OS)
is the program which starts up when you turn on your computer and runs underneath all other programs. Without it nothing would happen at all.
When you log on locally, you are presented with graphical environment.
You start at a graphical log in screen. You must enter your username and password. You also the have the option to choose from a couple session types. Mainly you have the choice between Gnome and KDE.
Once you enter in your username and password, you are then presented with a graphical environment that looks like one of the following...
You also have access to some UNIX servers as well.
-You can logon from virtually any computer that has internet access whether it is Windows, Mac, or UNIX itself.
In this case you are communicating through a local terminal to one of these remote servers.
– All of the commands actually execute on the remote server.
– It is also possible to open up graphical applications through this window, but that requires a good bit more setup and software.
Performs the function in a system wide basis. The function can be of any auxiliary kind but they are vital in controlling the computational environment of the system.
Example Print spooling, Network Management.
Once created Daemon process can exist throughout the life time of the Operating System.
This system call create new process.
This system call used after a fork to replace the process memory space with a new program.
This system call moves a process off the ready queue until the termination of the child.
is a file on the system that contains data, text, or program instructions. In this tutorial, you look at working with ordinary files.
store both special and ordinary files. For users familiar with Windows or Mac OS, UNIX directories are equivalent to folders.
provide access to hardware such as hard drives, CD-ROM drives, modems, and Ethernet adapters. Other special files are similar to aliases or shortcuts and enable you to access a single file using different names.
Grants the capability to read ie. view the contents of the file.
Grants the capability to modify, or remove the content of the file.
User with execute permissions can run a file as a program.
By default, every process that you start runs in the foreground. It gets its input from the keyboard and sends its output to the screen.
runs without being connected to your keyboard. If the background process requires any keyboard input, it waits.
The advantage of running a process in the background is that you can run other commands; you do not have to wait until it completes to start another!
Ending a process can be done in several different ways. Often, from a console-based command, sending a CTRL + C keystroke (the default interrupt character) will exit the command. This works when process is running in foreground mode.
If a process is running in background mode then first you would need to get its Job ID using ps command and after that you can use kill command to kill the process.
Multics (Multiplexed Information and Computing Service)
is an influential early time-sharing operating system. The project was started in 1964 in Cambridge, Massachusetts. The last known Multics installation running natively on Honeywell hardware was shut down on October 30, 2000, at the Canadian Department of National Defence in Halifax, Nova Scotia, Canada. Virtually all modern operating systems are heavily influenced by Multics, through Unix, either directly (Linux, OS X) or indirectly (Microsoft Windows).
is a general-purpose, imperative computer programming language, supporting structured programming, lexical variable scope and recursion, while a static type system prevents many unintended operations.
Versions of UNIX
ADVANTAGES AND DISADVANTAGES