Operating System OS Basics Operating System Basics Software

Operating System (OS) Basics

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

Examples of Software Applications n n Word processor Web browser E-mail client Multimedia player

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

Examples of Hardware n n n CPU RAM Keyboard Mouse Monitor

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

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

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

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

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

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

Multi-processing/Multi-tasking n Memory allocation ¡ n Time-slicing ¡ n Load program from hard drive into a section of memory (RAM) 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 n What do you think happens when you run too many programs and all of the memory is used up?

Virtual Memory Terms n Paging / Swapping ¡ n 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? n Mac OS X vs. i. OS Ubuntu Linux vs. Android n Advantages? n

How does the OS represent hardware devices? n n n 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 n n How does the OS know “when” to communicate with hardware? Interrupt vs. Polling ¡ What do you think they mean?