Transcript What is an operating system

Operating System Software
CS 1
Rick Graziani
Fall 2006
Operating System Software
• Why are operating system software so important?
• Was Windows 95 a breakthrough for PCs? Why?
• Why was Apple shopping for a new operating system and why did it
•
decide on Mac OSX?
Why is Microsoft worried about Linux?
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What is an operating system (OS)?
Operating System Software
Software which manages the overall operation of the computer system
including:
• hardware (CPU, RAM, I/O)
• security
• system interface
• application interface
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What is an operating system (OS)?
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What is an operating system (OS)?
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The User’s View
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What “is” an operating system?
Software files (programs) which are stored on the hard disk
• kernel with the internal programs
• external programs
Supporting Data Files
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The kernel
The operating system software file (program) which is copied into
RAM, usually from the hard disk drive, during the boot-up.
The kernel remains in RAM while the computer is on and is in
charge of the overall operation of the computer system.
The kernel contains the “internal programs” for the most often used
operations like copying files.
• kmem (Linux)
• command.exe (Microsoft)
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The functions of an operating system
1. Manages and Interacts with Computer Hardware
2. Provides and Manages System Security
3. Provides the System Interface
4. Provides the Interface for Application Software
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1. Manages and Interacts with Computer Hardware
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Manages the CPU
- What software programs the
CPU works on and when
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Manages RAM
- What is stored in RAM and
where it is stored
- Virtual memory
- OS will send message when
RAM is full
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1. Manages and Interacts with Computer Hardware
(continued)
• Provides the interface for
storage devices and manages
how data is stored on those
devices
- in charge of formatting disks
- creates sectors and clusters
- creates F.A.T. or V.T.O.C.
- sends message when disk is
full or there is some other
problem with writing data to
the disk
- virtual memory
- CD-ROM, DVD-ROM
- Flash drive
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1. Manages and Interacts with Computer Hardware
(continued)
•
Provides the Interface for Input
and Output Devices
– keyboard, mouse, printer,
– device drivers = software
programs which allow the
hardware device to be used
by the operating system and
by application software
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Manages the CPU processing time and priority
Processing Applications
multitasking = ability of the operating system run multiple software
programs (only one programs gets processed at a time)
multiprocessing = ability of the operating system to run multiple software
programs at the same time
Number of users with simultaneous access
multiuser = ability of the operating system to allow multiple users access
to the same computer at the same time
single user = the operating system only allows a single user at a time
access to the computer
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Multitasking and Multiprocessing
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Single-user Operating Systems
•
Windows XP
Only one user has access to the computer system at a time
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Multiuser Operating Systems
• Found on mainframes, minicomputers and microcomputers
• Terminals or other computers (PCs, Macs) connected to the
•
server
server = a computer which processes information (CPU and
RAM) , stores information (hard disk), and/or provides access to
peripheral devices (printers) for multiple users
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The OS also plays a part!
Amount of RAM recognized by the Operating System
• Windows 95: 1GB
• Windows 98: 1GB
• Windows 98SE: 1GB
• Windows ME: 1.5GB
• Windows NT: 4GB
• Windows 2000 Professional: 4GB
• Windows XP Home: 4GB
• Windows XP Professional: 4GB
• OS X: 8GB due to current hardware limitations
• OS 9.x: 1.5GB (no single application can utilize more than 1GB)
• Linux: 64GB
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Virtual Memory
Virtual Memory (VM) = the ability of the CPU and the operating
system software to use the hard disk drive as additional RAM when
needed (safety net)
Good – no longer get “insufficient memory” error
Bad - performance is very slow when accessing VM
Solution
= more RAM
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Virtual Memory
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Examples of Multiuser Operating
Systems
Linux/UNIX
• MAC OS X
• Red Hat Linux
• SUN UNIX
Microsoft NT, 2000
And many others, mostly on mainframes and minicomputers
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Advantages/Disadvantages of Multiuser Operating
Systems
Advantages
• Central location for the
installation and administration
of all software and data
• More cost effective - less
expensive than multiple
computers (PCs, Macs)
Disadvantages
• Single source for possible
problems
• Loss of individual user control
of their own software, data, and
peripherals
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2. Provides and Manages System Security
Single-user Operating Systems
• minimal security
• user has full authority
Multiuser Operating Systems
• login and password capability
• protection of user’s data
stored on the server’s central
hard disk drives
• protection and security for
software programs
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3. Provides the System Interface
System Interface or shell = the
interface between the user and
the computer
Command Line Interface (CLI)
• UNIX, DOS, older OS’s
Graphical User Interface (GUI)
• Macintosh OS, Windows 3.x,
Windows 95, Windows XP, XWindows, GNU, GNOME, Sun
OS
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Command Line Interface
DOS, UNIX, others
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DOS plus Windows 3.1
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Windows 95
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Windows XP
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Macintosh
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Mac OS X
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UNIX with X-Windows
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4. Provides the Interface for Application Software
•
Operating systems are software
• Operating systems are designed
and developed for a specific CPU
or “family of CPUs”
– Macintosh OS: Motorola
680xx, PowerPC Gx, Intel
– DOS: Intel CPUs
– Windows 9x and XP: Intel
80386, 80486, and Pentium
CPUs
– Linux: Intel CPUs
– MS NT & 2000: Intel CPUs
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4. Provides the Interface for Application
Software (continued)
•
Application software is developed
for an operating system
MS Word for Windows XP
• Windows XP
• Intel CPU
MS Word for the Macintosh
• Macintosh OS X
• Gx CPU or Intel CPU
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Compatibility
Question
Will software developed for one operating system work on another?
Will MS Word for Macintosh run on a PC with Windows XP?
Answer
No (unless there is special emulation software or hardware). The
software must be developed separately for each operating
system.
Much of this is beginning to change with MAC using the Intel CPU.
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Order of Development
1. The CPU
2. Other Hardware Components
3. Operating System Software
4. Application Software
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Preemptive Multitasking vs Cooperative Multitasking
Cooperative Multitasking
OS gives CPU processing
time to other programs at a
logical point, usually during
idle time
Preemptive Multitasking
OS allocates CPU time
between the different
programs based on amount
of time and priority of the
software application
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Multiprocessing with Multiple CPU’s
Asymmetric Multiprocessing = Tasks are assigned to a specific
CPU and each CPU has its own RAM memory
Symmetric Multiprocessing = Tasks are assigned to any
available CPU and CPU’s can share RAM memory
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Microsoft Windows Operating Systems
•
http://www.microsoft.com/windows/default.mspx
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Microsoft Windows Vista
• http://www.microsoft.com/windowsvista/default.mspx
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Glass and
Animations
• Windows are translucent, meaning that it's easier to focus on the
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content of a window rather than the window itself.
This feature (along with other window design enhancements on all
Windows Vista computers) reduces distraction and streamlines your
work while making windows easier to manage.
New scalable thumbnails are used throughout Windows to show you
the actual first page for documents, the actual photo for photos, a
screen capture for videos, and album art for individual songs.
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Windows Sidebar
• Windows Sidebar connects your desktop "gadgets"-mini-applications.
• For example your gadgets might include local weather, a photo
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slideshow, a dictionary, news headlines.
Gadgets are organized in an easy-to-use panel-the Windows Sidebarthat discreetly docks on the side of your Windows desktop.
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Folders & Virtual
Folders
• Virtual Folder, which is simply a saved search that is instantly run
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when you open the folder.
Subsequently, any time you click on this Virtual Folder, Windows Vista
runs the search and provides results almost immediately.
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Quick Search Box
and Column
Headers
• The Explorer Quick Search box and Column Header controls help
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you efficiently narrow down large selections of data.
With the Quick Search Box, you can start typing the name or the first
few letters of any displayed property, and the displayed files quickly
filter down to just the matching terms.
The dynamic new Column Header drop down menus let you easily
choose your filter values.
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Reliability
• Applications written for Windows Vista will keep running-with less
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chance of hanging or becoming unresponsive than with earlier versions
of Windows.
Windows Vista is measurably more resilient to application problems
and can recover better from problems that do occur.
Built-in diagnostics can proactively detect problems with system
components such as hard disks, memory, and networks.
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Security
• Set of parental control features, providing powerful tools to help
parents monitor, manage, and administer their children's computer
usage to keep them safe.
• User Account Protection which bridges the gap between user and
administrative privileges by allowing you to run applications under a
standard user account.
– When you need to perform an administrative task, such as install
software or drivers, Windows Vista prompts you to confirm your
intentions or to provide your credentials.
• Theft or loss of corporate intellectual property is an increasing concern
for organizations.
– Improved support for data protection at the document, file, directory,
and machine level.
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Linux
• http://www.linux.com/
• http://www.linux.org/
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www.linux.org
• Initially created as a hobby by a young
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•
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student, Linus Torvalds, at the
University of Helsinki in Finland.
Linus had an interest in Minix, a small
UNIX system, and decided to develop
a system that exceeded the Minix
standards.
He began his work in 1991 when he
released version 0.02 and worked
steadily until 1994 when version 1.0 of
the Linux Kernel was released.
The kernel, at the heart of all Linux
systems, is developed and released
under the GNU General Public License
(GNU's Not Unix!', see recursive
acronym).
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www.linux.org
• Its source code is freely
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available to everyone.
It is this kernel that forms
the base around which a
Linux operating system is
developed.
There are now literally
hundreds of companies and
organizations and an equal
number of individuals that
have released their own
versions of operating
systems based on the Linux
kernel.
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www.linux.org
• Apart from the fact that
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it's freely distributed,
Linux's functionality,
adaptability and
robustness, has made
it the main alternative
for proprietary Unix and
Microsoft operating
systems.
IBM, Hewlett-Packard
and other giants of the
computing world have
embraced Linux and
support its ongoing
development.
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www.linux.org
• More than a decade after its
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•
initial release, Linux is being
adopted worldwide as a
server platform primarily.
Its use as a home and office
desktop operating system is
also on the rise.
The operating system can
also be incorporated directly
into microchips in a process
called "embedding" and is
increasingly being used this
way in appliances and
devices.
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Organizing Files and Directories
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Organizing Files and Directories
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Operating System Software
CS 1
Rick Graziani
Fall 2006