Transcript Operating System Theory Guide to Operating Systems

Operating System Theory
Guide to Operating Systems
Third Edition
Objectives
After reading this chapter and completing the
exercises you will be able to:
• Understand how an operating system works
• Describe the types of operating systems
• Understand the history of operating system
development
• Discuss single-tasking versus multitasking
• Differentiate between single-user and multiuser
operating systems
• List and briefly describe current operating systems
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Understanding Operating
Systems
• Operating system (OS)
– Set of basic programming instructions to computer
hardware
• Forms layer of programming code on
which most other functions of the
computer are built
• Desktop operating system
– Typically installed on a PC type of computer used
by one person at a time
• Computer may or may not be connected
to a network
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Understanding Operating
Systems (continued)
• Server operating system
– installed on a more powerful computer that is
connected to a network
– act in many roles to enable multiple users to
access information, such as electronic mail,
files, and software
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Understanding Operating
Systems (continued)
• Input/output (I/O)
– Basic functions which let other programs easily
talk to the computer hardware
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Understanding Operating
Systems (continued)
• Operating systems perform the following
tasks:
– Handle input from the keyboard, mouse, and
other input devices
– Handle output to the monitor and printer
– Handle communications using a modem
– Handle network communications, such as for a
local network and the Internet
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Understanding Operating
Systems (continued)
• Operating systems perform the following
tasks (continued):
– Control input/output for devices such as a
network interface card
– Control information storage and retrieval using
various types of disk and CD-ROM drives
– Enable multimedia use for voice and video
reproduction, such as playing music through
speakers
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Understanding Operating
Systems (continued)
• Communicates directly with all of these
devices
• Exchange information with specific hardware
(chips) inside the computer
– Code (instructions) for this exchange is typically
referred to as a device driver
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Understanding Operating
Systems (continued)
• A device driver translates computer code to
display a screen, or translates movements of
a mouse into action
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Understanding Operating
Systems (continued)
• A separate device driver is usually present for
each individual device inside the computer
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Understanding Operating
Systems (continued)
• A good example of a device is a compact
disk read only Memory (CD-ROM) drive
• Device drivers that interface with your OS for
other devices, include:
– Floppy and hard disk drives
– Computer monitors
– Keyboards
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Understanding Operating
Systems (continued)
• Device drivers that interface with your
OS for other devices, include:
– Mouse and trackball devices
– Modems
– Printers and scanners
– Others are shown on page 5 of the textbook
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Understanding Operating
Systems (continued)
• Communicates with the application software
running on the computer
– See Figure 1-3
• Application software
– Vague term; it can mean a word processor, spreadsheet,
database, computer game, etc
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Understanding Operating
Systems (continued)
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Understanding Operating
Systems (continued)
• Essential step to start a computer
– Load the Basic Input/Output System or BIOS
• Every PC has a BIOS stored in Read Only Memory
or ROM
• Sample BIOS setup screen
– See Figure 1-4
• Turn on a PC
– Jumps to a startup program inside the BIOS
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Understanding Operating
Systems (continued)
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Understanding Operating
Systems (continued)
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Understanding Operating
Systems (continued)
• Elements in Figure 1-5 include the following:
– Application software
– API (Application Program Interface)
– BIOS
– Operating system kernel
– Device drivers
– Resource managers
– Optional drivers
– Computer hardware
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Understanding Operating
Systems (continued)
• Common features of operating systems:
– Interface between the computer hardware and
application programs
– Act as an intermediary between the user and
applications
– User interface into computer hardware and application
programs
– Manage memory and central processor use
– Manage peripheral devices
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Types of Operating Systems
• Functions of a computer
– Dictate what the OS will do and how it will do it
• An example
– Microwave oven needs device drivers for the LED (Light
Emitting Diode) display, numeric keypad, and door close
switches
• Operating systems are organized by:
– Size, type, and purpose of the computer they run on
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Types of Operating Systems
(continued)
• PC-class computers
– Designed for individual users to perform tasks
• Example of complexity of PC operating
systems
– Windows 95 had one millions lines of code
– Windows XP has 50 million
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Types of Operating Systems
(continued)
• Two main groups of computers
– Older, large computers with traditional operating
systems
– Newer, smaller hardware with specialized
operating systems
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Time Sharing
• Mainframe-class computers
– Conduct massive calculations or manipulate huge
amounts of data
• These systems are referred to as
– Time-sharing systems
• Time-sharing systems frequently conduct what
are termed batch processes
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Time Sharing (continued)
• Sequential processing
– Each process request is completed and the data
returned before the next process is started
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Time Sharing (continued)
• Time-sharing mainframe accessed by cables from
terminals to a communications box connected to the
mainframe, creating a multiuser system
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Real-time Systems
• Real-time systems
– what most of us are familiar with today
• PC-based operating systems
– such as Windows XP and Mac OS X
– interact directly with the user—even
multiple users and respond in real time
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Real-time Systems
(continued)
• Server running an OS such as NetWare to provide
real-time access to multiple users over a network.
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Multiuser Systems
• Multiuser environment
– Multiple users can do many different things on the
machine at the same time
– All users are using one machine or a group of
machines to do all their work
• Client/server system
– Newest types of large computing and operating
system environments
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Multiuser Systems (continued)
• Client/server operations
– Macintosh computer running Mac OS
– Minimally configured Windows XP computer
connected to a network that includes a Windows
2000 or 2003 server
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A Short History of Operating
Systems
• Computers used as large automated calculators
• Extremely large, often taking up entire rooms
• Scientists programmed computers to perform
precise tasks
• Operating systems were rudimentary
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A Short History of Operating
Systems (continued)
• I/O devices were created, and computer memory
capacity and speed increased
• Ability to share computer resources among various
programs
• OS evolution in this era are long lost
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A Short History of Operating
Systems (continued)
• Notable players responsible for setting the stage
for the full-featured functionality
– Digital Equipment Corporation’s PDP series computers
– Original UNIX was developed at AT&T Bell Labs in 1969
by Kenneth Thompson and Dennis Ritchie
– DEC VAX computers used VMS
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A Short History of Operating
Systems (continued)
• Mid sixties, a simple programming language was
developed
– Dubbed BASIC, or Beginner’s All-purpose Symbolic
Instruction Code
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A Short History of Operating
Systems (continued)
• 86-DOS
– Written by Tim Patterson for the new 8086
microprocessor
– Evolved in 1980 into the Microsoft Disk Operating
System, or MS-DOS
• IBM introduced the first PC in 1981
– Caused a revolution, because it was designed
around an “open standard”
– Anyone was welcome to make PCs that worked
like IBM’s PC, or hardware that would work with it
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A Short History of Operating
Systems (continued)
• The Macintosh was introduced and it seemed to be
light years ahead of the IBM PC
– Came with a standard graphical user interface (GUI)
– MS-DOS was still text-based
– Managed the computer memory closely for the software
• Microsoft, however, did not stay behind for long
– In 1990, Microsoft introduced Windows which provided a
GUI and many of the same functions as the Mac OS
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Single-Tasking versus
Multitasking
• Multitasking
– Technique that allows a computer to run two or more
programs at the same time
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Single-Tasking versus
Multitasking (continued)
• Most PCs have only one CPU chip
– does one thing at a time
– multitasking is achieved by splitting processor time
between applications
– switching so rapidly that the user is not aware of any
discontinuity
• There are two general types of multitasking
– cooperative multitasking shown in Figure 1-8
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Single-Tasking versus
Multitasking (continued)
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Single-Tasking versus
Multitasking (continued)
• Operating system
– hands over control to a program
– sits back
– waits for the program to hand control back to the
operating system
• Preemptive multitasking
– illustrated in Figure 1-9
– OS is in control of the computer at all times
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Single-Tasking versus
Multitasking (continued)
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Single-Tasking versus
Multitasking (continued)
• A single-tasking operating system
– Executes one program at a time (see Figure 1-10)
– To do something else, one program must be stopped,
and a new program must be loaded and executed
– New single-tasking operating systems are found only in
computers with very limited processor capacity, such as
Personal Digital Assistants (PDAs)
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Single-Tasking versus
Multitasking (continued)
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Single-Tasking versus
Multitasking (continued)
• Task-switching operating system
– offers many of the device management functions of
the multitasking operating system
– can load multiple application programs at once
– figure 1-11 illustrates the concept of task switching
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Single-Tasking versus
Multitasking (continued)
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Single-User versus
Multiuser Operating Systems
• Multiuser operating systems
– run multiple programs at the same time
– allow multiple users to use an application
simultaneously
– most use preemptive multitasking technology
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Single-User versus
Multiuser Operating Systems
Desktop operating systems covered in this book
– initially were designed as single-user systems
– exceptions are UNIX and Linux - multi-user OS by
design
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Current Operating Systems
• Operating systems in this book are the most
common in today’s computing environments:
– Windows 2000 Professional and Server
– Windows XP (Home, Professional, Tablet PC, and Media
Center)
– Windows Server 2003
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Current Operating Systems
• Operating systems in this book are the most
common in today’s computing environments
(continued):
– The different flavors of UNIX/Linux operating systems,
focusing particularly on Red hat Enterprise Linux 3.0
– NetWare 6.x
– Apple Macintosh Mac OS X (version 10.3 or Panther)
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Summary
• An operating system provides the foundation upon
which to run the components of a computer and
execute applications
• Two common types of operating systems
– Desktop - may or may not be a network operating
system
– Server - always a NOS
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Summary (continued)
• Device drivers can extend the native functions to
provide access and control over different types of
devices\
– Printers
– CD-ROM drives.
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Summary (continued)
• BIOS
– Low-level program code that operates between the
computer hardware and a higher level operating system
– Initiate communications with hardware devices
– Perform hardware tests at startup
– Enable the startup of the higher-level operating system
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Summary (continued)
• Operating system may be geared to run a large mainframe
or a small PC-type of computer. However, the small PCtype systems now can be very powerful and are used in
many places instead of mainframe systems.
• Operating systems can be understood in terms of
characteristics
– Time sharing, real-time operation, and multiuser
capabilities
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Summary (continued)
• History of operating systems and computers
– Progression from physically huge computers
– Large computers
– Desktop-sized computers that have powerful processing
capabilities and operating systems
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Summary (continued)
• From the standpoint of the user
– The most significant advances in operating systems
is the GUI
• Early operating systems tended to be singletasking, but modern systems are largely
multitasking.
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Summary (continued)
• A true multiuser system
– Multiple users access and run a single application on a
single computer at the same time
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Summary (continued)
Currently popular operating systems are the topic of
this book
– Windows 2000/XP/Server 2003
– UNIX/Linux
– NetWare 6.x
– Mac OS X
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