Operating System (OS)  A computer program that manages the hardware and software resources of a computer. controlling and allocating memorycontrolling and allocating memory prioritizing system requestsprioritizing system requests controlling input and output devicescontrolling input and output devices facilitating networkingfacilitating networking managing files.managing files.

Operating System (OS)

MAC OS X

Operating System (OS) Linux

Graphical user interface (GUI)  GUI, often pronounced "gooey.”  A particular case of user interface for interacting with a computer which employs graphical images and widgets in addition to text to represent the information and actions available to the user.

Unix  Unix (officially trademarked as UNIX™) is a computer operating system originally developed in the 1960s and 1970s by a group of AT&T employees at Bell Labs.

Why Unix ?  Platform independent Unix is more flexible and can be installed on many different types of machines, including main-frame computers, supercomputers and micro- computers.Unix is more flexible and can be installed on many different types of machines, including main-frame computers, supercomputers and micro- computers.  Stable Not often goes down like Windows does, so requires less administration and maintenance.Not often goes down like Windows does, so requires less administration and maintenance.

Why Unix ?  Reliable Unix has greater built-in security and permissions features than Windows.Unix has greater built-in security and permissions features than Windows.  Free Open-source Operating systemOpen-source Operating system  Any computer software whose source code is available under a license that permits users to study, change, and improve the software, and to redistribute it in modified or unmodified form.

UNIX system layers

Kernel?  The central component of most computer operating systems (OSs).  Its responsibilities include managing the system's resources and the communication between hardware and software components.

Kernel?

Shell?  A Unix shell, also called "the command line", provides the traditional user interface for the Unix operating system and for Unix-like systems.  Users direct the operation of the computer by entering command input as text for a shell to execute.

Shell?  Samples of UNIX shells Bourne shell (sh)Bourne shell (sh) Korn shell (ksh)Korn shell (ksh) C shell (csh)C shell (csh)

UNIX directory tree

 / Root directory on some systemsRoot directory on some systems  /bin binary files (program files)binary files (program files) EX. ls, mkdir, rm, etc.EX. ls, mkdir, rm, etc.  /boot or /kernel information for booting the system, directory for storing (the) kernel(s).information for booting the system, directory for storing (the) kernel(s).

UNIX directory tree  /dev entries for all devices.entries for all devices.  /etc system configuration files, startup and shutdown procedures.system configuration files, startup and shutdown procedures.  /home (or /export/home or /users on some systems): user home directories(or /export/home or /users on some systems): user home directories

UNIX directory tree  /lib library fileslibrary files  /etc entries for network systemsentries for network systems  /opt third party software (used to be /usr/local), unbundled softwarethird party software (used to be /usr/local), unbundled software

UNIX directory tree  /var Variable data. Data files that are continually being re-created or updated.Variable data. Data files that are continually being re-created or updated.  /src These are sources to the kernel or locally built packages.These are sources to the kernel or locally built packages.  /tmp Temporary files. A convenient place for a running program to create a file for temporary use.Temporary files. A convenient place for a running program to create a file for temporary use.

Basic UNIX commands  Directory commands cdChange the working directory findFind a file by name or by other characteristics mkdirMake a directory rmdirRemove a directory  File manipulation commands catDisplay a file chmodChange the permissions mode of a file chownChange the owner and/or group of a file cpCopy a file diffDisplay differences between pairs of text files grepSearch a file for a specific text string mvMove or rename a file rmRemove a file

Basic UNIX commands  Display commands datePrint the date and time fingerDisplay information about a user headDisplay the first few lines of a file lessBrowse a text file lsList the contents of a directory manDisplay a reference manual page moreDisplay a text file pwdDisplay the working directory pathname tailDisplay the end of a file whoDisplay who is on the system  Process commands exitTerminate a process killTerminate or send a signal to a process passwdCreate or change a password psDisplay the status of a process telnetConnect to a remote system using the Telnet protocol

Basic UNIX commands  Commands in UNIX are case- sensitive.  File name cannot have space in- between, otherwise UNIX will separate into different files.

VI: UNIX text editor  Vi is a screen-oriented text editor computer program written by Bill Joy in 1976 for an early BSD release.

VI: UNIX text editor

 Insert mode [i]  Command mode [:] Ex.:q exit from viEx.:q exit from vi :wsave file :set numbershow line number