Operating System (OS) Basics

Operating System Basics Software (applications) Operating System (OS) Hardware

Examples of Software Applications Word processor Web browser client Multimedia player

Examples of Operating Systems MS-DOS Windows XP Windows 7 Mac OS X Ubuntu Linux

Examples of Hardware CPU RAM Keyboard Mouse Monitor

Operating System Basics Operating System (OS)  Provides user interface(s) WIMP! Windows, Icons, Menus, Pointer (mouse)  Interfaces directly with the hardware e.g., device drivers Input devices Ouput devices  File management  Monitors and manages system activities

Graphical User Interface (GUI) Name GUI elements in applications Name GUI elements in an OS

Where does input come from? keyboard mouse tablets scanning pens OCR – Optical Character Recognition MICR – Magnetic Ink Character Recognition Webcam microphone Etc.

...and output? monitors (CRT, LCD, etc.) printers speakers Braille output monitors

File management Create files Delete files Search for files Move files Navigate file tree Create folders Etc.

More OS Functions Communicating with peripherals  keyboard, mouse, monitor, printer, etc. Coordinating concurrent processing  multiple programs (processes) running at the same time Memory management  each program has their own space in memory Resource monitoring  processor time, memory usage, etc. Accounting and security  users, permissions, security logs, etc. Program and data management  programs reading/writing to files

Multi-processing/Multi-tasking Memory allocation  Load program from hard drive into a section of memory (RAM) Time-slicing  Giving a particular program a “slice” of time to run Priority  A program can be given “priority” if it’s more important (e.g. window in focus)

Virtual Memory What do you think happens when you run too many programs and all of the memory is used up?

Virtual Memory Terms Paging / Swapping  Moving program data between memory and disk Where do you see this stuff?  pagefile.sys in windows  /swap space in linux  Whenever you use up all your RAM and your hard drive goes crazy.

Discussion: Why are there different operating systems? Mac OS X vs. iOS Ubuntu Linux vs. Android Advantages?

How does the OS represent hardware devices? Hardware complexities are hidden from the user by the OS Hardware is simplified and represented virtually by the OS Examples  Mouse pointer  File tree and drive letters  Others?

OS  Hardware Communication How does the OS know “when” to communicate with hardware? Interrupt vs. Polling  What do you think they mean?