Operating System: Components, Functions and Types

Components of an OS

• The three elements of an Operating System are:
  • User Interface: The part of the OS interacted with
  • Kernel: The core of the OS that interacts with the BIOS and the UI.
    • The kernel interacts with the BIOS at one end, and the UI at the other end
  • File Management System: Organizes and manages files

OS Functions

• Operating Systems provide:
  • File Management
  • Application Management
  • Built-in Utility Programs
  • Control of Computer Hardware

Types of Operating Systems

• Multiuser OS allow two or more users to work with the computer at the same time
• Multitasking allows for two or more processes to run at the same time
• Multithreading allows for two or more parts of the same process to run at the same time

PC Operating Systems

• Examples of PC Operating Systems include:
  • Microsoft Windows
  • Macintosh OS
  • Linux

MS Windows Versions

• Windows has been released in Home (Non-Professional) Versions
  • Windows 95
  • Windows 98
  • Windows ME
• Windows has been released in Professional (Business) Versions
  • Windows NT
  • Windows 2000
• The two lines of Windows versions came together in Windows XP (2001)

Disk Operating System (DOS)

• DOS was the first PC Operating System, released in 1981
• DOS is not a multitasking OS, only one program could run at a time
• DOS has a command-line interface and no GUI
• Early versions of Windows sat on top of DOS and therefore used DOS to communicate with the BIOS
• Windows XP communicates directly with the BIOS, but allows commands to be entered via a command prompt

File System

• A file is a collection of bytes of information treated as a single unit
• Every file is given a name to make it easy to find and use later
• The file system keeps track of where a is actually resident on a disk
• A disk (hard disk, floppy, optical disk) is subdivided into directories or folders
• The top level folder on a disk is known as the root
• The root is generally subdivided into subfolders
• Any folder or subfolder can contain files and other folders
• The fully-qualified filename includes the name of the file and the path to the folder in which it resides. For example: c:\courses\061\cit141\chapter4.ppt
• A particular file extension can be registered and associated with a particular program
  • .docx files are associated with MS Word
  • .xlsx files are associated with MS Excel
  • .txt files are associated with Notepad
  • .html files are associated with IE
• Windows knows what to do when a file in My Computer is double-clicked based on the file extension
• Each file has four attributes which can be viewed or set:
  • Read Only: A file may be viewed, copied, executed (if appropriate), but not changed; it can be deleted
  • Hidden: A file will not be displayed in a normal list of files
  • System: A file is identified to belong to the system and should not be modified
  • Archive: A file is or isn't a candidate for backup

DOS Commands

• DOS Commands are of two types, Internal and External:
  • Internal commands are resident in the main kernel file: command.com (or cmd.exe)
  • External commands are separate little programs
• DOS commands are important because scripts can be written to execute a set of commands automatically
• The command prompt reminds you of the current drive and the current directory by default
• Three Parts of a DOS Command:
  • Command Name
  • Switches
  • Parameters
• DOS Wildcard Characters include ? and * which can be used to affect multiple files with a single command
  • The ? stands for any single character:
    • copy c:\temp\notes??.doc d:\temp means copy any Word file that begins with the word "notes" with exactly two other characters, like "notes01.doc" or "notesAB.doc"
  • The "*" wildcard replaces any number of characters.
    • For example: copy c:\temp\notes.* d:\temp (copy all files with the name "notes" and any extension.)
    • copy *.doc c:\temp (copy all files with a "doc" extension in the current directory.)

DOS Commands

• At the Command Prompt:
  • A drive letter and a ":" (e.g. "f:") makes that your current drive
  • CD (Change Directory)
    • cd (with no parameters) Reminds you what the current Directory is
    • cd .. Moves you to the parent of the current directory (up one level)
    • cd \ Moves you to the root of the current drive
    • cd Makes that your current directory
• More DOS Commands:
  • MD: Make Directory
  • RD: Remove a directory or an entire directory tree
  • DIR: Display the contents of a directory
  • DEL (or ERASE): Deletes one or more files
  • COPY: Places a copy of file(s) in a different folder
  • XCOPY: Flexible copy command used for copying large groups of files, commonly used for file backup
  • MOVE: Moves file(s) from one folder to another
  • REN: Rename files
  • ATTRIB: Displays or sets file attributes
  • FORMAT: Formats a disk
  • CHKDSK: Tests the file system on a disk, and reports status
  • DATE and TIME: Display & set the current date & time in the PC
  • TYPE: Displays the contents of a text file

Overview of operating system components, functions, and types, including multiuser, multitasking, and multithreading. Also covers PC operating systems such as Windows, Macintosh OS, and Linux.