Operating Systems

Unit 3 Processing Data Operating System

What is an Operating System? Operating system goals: A program that acts as an intermediary between a user of a computer and the computer hardware. Execute user programs and make solving user problems easier. Make the computer system convenient to use. Use the computer hardware in an efficient manner.

Operating System Definition OS is a resource allocator Manages all resources Decides between conflicting requests for efficient and fair resource use OS is a control program Controls execution of programs to prevent errors and improper use of the computer

System Resources System Resources

Hardware Components

Software

System Software

Application Software

Operating Systems Types – Basic Terminology Multi-user – Two or more users running programs and sharing peripheral devices, such as a printer, at the same time. Multi-tasking – A computer's capability to run multiple applications at the same time. Multi-processing – Allows a computer to have two or more CPUs (Central Processing Unit) that programs share. Multi-threading – The capability of a program to be broken into smaller parts that can be loaded as needed by the OS. Multithreading allows individual programs to be multi-tasked. Today, almost all operating systems are multi-user, multi-tasking, and support multi-threading.

Different Types of Operating Systems Single-user, single-process operating systems: Allow only one user at a time to use the computer system. The user can execute/run only one process at a time. Examples: DOS, Windows 3.1 Single-user, multi-process operating systems: Allow a single user to use the computer system. However, the user can run multiple processes at the same time. Example: OS/2

Different Types of Operating Systems Multi-user, multi-process operating systems: allow multiple users to use the computer system simultaneously. Each user can run multiple processes at the same time. Examples: UNIX, Windows XP

What the Operating System Does

The operating system controls: Communication with peripherals Coordination of concurrent processing Memory management Monitoring of resources and security Management of programs and data Coordinating network communications

Popular Operating Systems Microsoft Windows 95, 98, ME – Windows is one of the most popular operating systems today. Windows is designed to run on PCs and to use an Intel-compatible CPU. Windows 9x systems are designed to be run and maintained by a single user. Microsoft Windows NT/2000/XP –Windows NT, 2000 and XP are operating systems that were designed to support multiple (concurrent) users and to run applications simultaneously. Both Windows NT and Windows 2000/XP have incorporated many networking features.

Disk Operating Systems Microsoft developed the Disk Operating System (DOS), also called MS-DOS, in 1981. DOS was designed then, for the IBM Personal Computer. Windows 98 and Windows 2000 both support DOS commands in order to address compatibility issues related with older applications. Simply put, DOS is a collection of programs and commands used to control the overall computer operation in a disk-based system.

Basic Elements of DOS The following are some of the basic things to remember when working with DOS. DOS is a command line operating system; it is not userfriendly. The best way to learn DOS is to use it. DOS can only run one program at a time. It is not multitasking. DOS can only run small programs and has memory limitations. DOS is an essential tool for IT professionals and is used extensively for troubleshooting.

DOS File Structure Programs and data are stored the same way a document would be filed in a folder in a file cabinet. In DOS, they are called files and are grouped together in directories. Directories are much like the folders in the file cabinet. Directories can be nested inside other directories, just like a folder placed inside another folder. Nested directories are referred to as subdirectories. Directories became known as folders in the Windows OS.

DOS Files A file is simply a block of logically related data, given a single name, and treated as a single unit, such as programs, documents, drawings and other illustrations, sound files, and so on. Files are referred to by filenames. In DOS, filenames can be up to 8 characters with an extension of 3 characters. (8 + 3) The extension is separated from the main portion of the filename by a period and it identifies what type of file it is. Example: nazim. txt

DOS Directory Structure Hard drives organize the disk into directories and subdirectories. The main directory is known as the root directory. All other directories, if they exist, then radiate (branch out) from the root directory, similar to the branches of a tree. Locating any given file requires knowledge of three things: the drive, directory and subdirectory in which the file is found.

DOS Directory Structure In MS-DOS, the format for specifying the path to a file is as follows: C:\directory name\subdirectory name\filename The first back slash indicates the root directory, which is present on all DOS disks The back slash (\) after each item signifies the presence of a directory or subdirectory

Basic DOS Commands In DOS, the main user interface is the command line. The command line is the space immediately following the DOS prompt, C:\> where C:\ represents the hard disk drive root directory, and '>' is known as the prompt. All the DOS commands are typed to the right of the prompt and executed by pressing the return (ENTER) key on the keyboard.

Basic DOS Commands

AUTOEXEC.BAT This file contains a batch of DOS commands that will automatically be carried out when DOS is loaded into the system. Examples of commands normally located in the Autoexec.bat file include: DATE – Causes DOS to prompt user for the date TIME – Causes DOS to prompt the user for the date and time DOSKEY – loads the DOSKEY

The User Interface: The Human-Machine Connection The user interface is what the user sees on the screen and interacts with Two major user interface types: Character-based interface Graphical user interface

A Character-Based User Interface MS-DOS or Unix The user interacts with characters… Letter Numbers Symbols Controls: ^C

Graphical User Interface (GUI) User interacts with GUI using… Windows Menus Toolbars Mouse Keyboard shortcuts

Computer System Structure Computer system can be divided into four components Hardware – provides basic computing resources CPU, memory, I/O devices Operating system Controls and coordinates use of hardware among various applications and users Application programs – define the ways in which the system resources are used to solve the computing problems of the users Word processors, compilers, web browsers, database systems, video games Users People, machines, other computers

Four Components of a Computer System

Computer Startup bootstrap program is loaded at power-up or reboot Typically stored in ROM or EPROM, generally known as firmware Initializates all aspects of system Loads operating system kernel and starts execution

Computer System Organization Computer-system operation One or more CPUs, device controllers connect through common bus providing access to shared memory Concurrent execution of CPUs and devices competing for memory cycles

Computer-System Operation I/O devices and the CPU can execute concurrently. Each device controller is in charge of a particular device type. Each device controller has a local buffer. CPU moves data from/to main memory to/from local buffers I/O is from the device to local buffer of controller. Device controller informs CPU that it has finished its operation by causing an interrupt.

Windows NT Introduced in 1993 Windows NT Workstation still used in architectural firms, audio and video production studios and graphics studios Microsoft stopped supporting Windows NT in 2001

Windows 9X Released in 1995, Windows 95 was the first member of the Windows 9x family Windows 98 considered to be an upgrade of Windows 95 Released in 2000, Windows ME was the last member of the Windows 9x family, still widely used, but considered by experts to be obsolete

Windows XP Released in 2001 Key goals for the system: portability security multiprocessor support extensibility compatibility with MS-DOS and MS-Windows applications.

Uses a micro-kernel architecture Available in four versions: Professional Server Advanced Server National Server

Depiction of XP Architecture

Windows 2000 Released in 2000 Combined the features of Windows 98 and Windows NT

Windows 2000 32-bit preemptive multitasking operating system for Intel microprocessors. Key goals for the system: portability security POSIX compliance multiprocessor support extensibility international support compatibility with MS-DOS and MS-Windows applications. Uses a micro-kernel architecture. Available in four versions, Professional, Server, Advanced Server, National Server.

LINUX Released in late 1990s New version of UNIX Distributed for free

History Linux is a modern, free operating system based on UNIX standards First developed as a small but self-contained kernel in 1991 by Linus Torvalds, with the major design goal of UNIX compatibility It has been designed to run efficiently and reliably on common PC hardware, but also runs on a variety of other platforms

Components of a Linux System

The Linux System Linux uses many tools developed as part of Berkeley’s BSD operating system, MIT’s X Window System, and the Free Software Foundation's GNU project The min system libraries were started by the GNU project, with improvements provided by the Linux community Linux networking-administration tools were derived from 4.3BSD code; recent BSD derivatives such as Free BSD have borrowed code from Linux in return The Linux system is maintained by a loose network of developers collaborating over the Internet, with a small number of public ftp sites acting as de facto standard repositories

Linux Distributions Standard, precompiled sets of packages, or distributions, include the basic Linux system, system installation and management utilities, and ready-toinstall packages of common UNIX tools

Design Principles Linux is a multiuser, multitasking system with a full set of UNIX-compatible tools Its file system adheres to traditional UNIX semantics, and it fully implements the standard UNIX networking model Main design goals are speed, efficiency, and standardization