Transcript Some operating systems, such as Windows, enable programs to

Operating Systems
By
Nanda Page
Operating System – Soul of
Computer
• Without the operating system, a computer
is only devices connected together…..
• Operating system brings life to computer
and get amazing tasks done!
Operating System
Fundamentals
1.
2.
3.
4.
5.
What is an OS
Components of an OS
Functions of an OS
Types of OS
Common Operating Systems
Operating System
The operating system (OS) is
software that controls the interaction
between hardware and user software
when the computer is switched on,
OS will first load into the main
memory
Operating System Objectives
• Human- Machine communication
• Convenience
– Makes the computer more convenient to use
• Efficiency
– Allows computer system resources to be used
in an efficient manner
• System protection and Error Handling
• Platform for user’s programs to execute
• Ability to evolve
Elements of an OS
• User Interface – The part of the OS that you interface with.
• Kernel – The core of the OS. Interacts with the Basic Input
Output System (at one end), and the User at the other end.
• File Management System – Organizes and manages files.
Types of Software
•
System Software- Performs essential operation tasks
– Operating system
– Utility programs
• A utility is a program that performs a task that is not typically
handled by the operating system.
• Some utilities enhance the operating system's functionality.
–
Data compression
–
Backup
–
Antivirus
–
Screen savers
•
Driver Programs (Device Driver)
– small program that allows a specific input or output device to
communicate with the rest of the computer system
Types of Software
• Application Software - Performs specific tasks
for users
– Business application
– Communications application
– Multimedia application
– Entertainment and educational software
Hierarchy of computer
software
The operating system's tasks
1. Booting a Computer
2. User-interface
3.Running Programs
4. Managing Files
5. Memory Management
6. Scheduling Jobs
7. Managing Devices
8. Establishing Internet
Connection
9. Controlling Network
10. Task Management
Computer’s Boot Sequence
• All of the components in your computer, such as the CPU, the hard
drive and the operating system, work together as a team.
• Memory is also one of the most essential parts of this team. From the
moment you turn your computer on until the time you shut it down,
your CPU is constantly using memory.
• When you turn on the computer, the electric signals make active the
processor chip. The processor loads the instructions stored in ROM.
These are the computer’s startup instructions called Firmware. It is
the BIOS (Basic Input /Output System), which is automatically
activated when’ computer is turned on and tests the computer
hardware. This type of testing is called Power-On Self Testing
(POST).
• Once the POST has successfully completed, the software loaded in
ROM will begin to activate the computer's disk drives. When the
computer activates the hard disk drive, it finds the first piece of the
operating system: the bootstrap loader.
OS in action..
• The computer loads the operating system (OS) from the
hard drive into the system's RAM. The most important
component of operating system is called the Kernel.
• The Kernel is the core of an operating system; It
performs various functions remaining inside the RAM,
such as management Of memory, input/output devices,
application programs etc. The Kernel is memory resident
program of operating system.
• Cold Boot
• Warm Boot
User-interface
• User interface means how the user interacts with the
computer to perform various tasks. The hardware
devices like keyboard, mouse and monitor etc. are used
for interfacing.
• click graphical objects on screen.
• Command-line user interface
• Graphical user interface.
GUI lets you control the
system by using a mouse.
Applications designed to run
under one operating system
use similar interface elements.
Icons
Program
running in
a window
Desktop
Window control buttons
Start menu
Start button
Taskbar
Dialog box
Running Programs
The operating system also provides the interface between
the programs and the user. Through program, the user
accesses other computer resources such as printer,
backing storages or another application programs.
Actually, in program the built-in instructions known as
“system calls” are used that request the services from the
operating system.
• Similarly, in data communication, information is sent and
received via operating system.
File System
The data and programs are stored permanently on the disk
for future use.
• A file is a collection of bytes of information treated as a
single unit.
• It is given a name to make it easy to find and use later.
• The file system keeps track of where a file is actually
resident on a disk.
• A disk (hard disk, floppy, optical disk) is subdivided into
directories or folders.
Managing Files
• The operating system keeps track of
all the folders and files and subfolders.
• The operating system maintains a list
of these folders and files in the
starting area of disk called the FAT
(File Allocation Table). The FAT is
created when the new disk is
formatted by Operating system.
• The FAT area of disk contains the
names of files, addresses of the disk
where the data or contents of the
respective files are stored.
Memory Management
•
•
•
•
The memory unit has very important role for data
processing.
High-speed cache -- This is fast, relatively small
amounts of memory that are available to the CPU
through the fastest connections. Cache controllers
predict which pieces of data the CPU will need next
and pull it from main memory into high-speed cache
to speed up system performance.
Main memory -- RAM.
Secondary memory – Permanent Storage
Virtual RAM –Part of hard disc under the control of
the operating system.
Hierarchy of Memory
Memory Management


The critical parts of the operating system are maintained in
RAM as long as the computer is on.
When you open an application, it is loaded into RAM.

Only the critical parts of an application are loaded in the
RAM to conserve its usage, and later when other pieces as
needed they are loaded one by one.

After an application is loaded, any files that are opened for
use in that application are loaded into RAM.

When you save a file and close the application, the file is
written to the specified storage device, and then it and the
application are removed from RAM.

The processor takes data and program instructions from
RAM during processing. system clears the memory area
allocated to that program and its data.
Memory Storage and
Management
• When an operating system manages the computer's
memory, there are two broad tasks to be accomplished:
• Each process must have enough memory in which to
execute, and it can not run into the memory space of
another process.
• The different types of memory in the system must be
used properly so that each process can run most
effectively.
Scheduling Jobs
• A job is an activity or operation that a processor
performs. It may be receiving data from input device,
sending output to output device or loading data from disk
into RAM etc.
• The operating system determines the order in which the
jobs are to be processed. Sometimes, the operating
system processes jobs on a first-come first- served
basis.
• But in some situations, one user may have higher priority
than the other users. In this case, the operating system
has to adjust the schedule.
• Sometimes, a device is busy in processing a job and
another job is sent to that device. For example, three
documents are sent to printer but the printer can print
only one document at a time. In this case, the operating
system places the other documents in buffers.
Configuring Devices
The functions of devices attached with
the computer are controlled by the
special system software called device
drivers. The device driver tells the
operating system how to communicate
with a device.
• A driver helps the operating system
communicate with the electrical signals
from computer hardware.
Connecting to Internet
• connection between your computer and
the ISP (Internet Service Provider)
Server.
• Some operating systems also have builtin browser program used to access the
information on Internet. The information
downloaded from the Internet is managed
by the operating system in RAM as well
as in the disk.
Controlling Network
• Some Operating systems are specially
developed, for networking-network operating
systems
• A network operating system organizes and coordinates multiple users and makes it possible to
access and share resources on network.
• Creating and deleting user accounts
• security features-Unauthorized
access & data security
• Resources on Network
Task Management
• A task is an operation such as storing, printing or
calculating etc.
• you are downloading information from the
Internet through browser, listening speech,
printing a document through word processing
program, entering data into a worksheet etc.
• Some operating systems, such as Windows,
enable programs to share information.
1
Information is clipped
from one application (Excel)
2
Using the clipboard Viewer to
examine the information
Pasting the information
into another application (WordPro)
3
Types of Operating Systems
• Single-user, single task - one user
can effectively do one thing at a time.
The Palm OS for Palm handheld
computers
• Single-user, multi-tasking - most
people use on their desktop and
laptop
computers.
Microsoft's
Windows and Apple's Mac OS
platforms
• Multi-user- Windows NT, Unix, VMS
and mainframe operating systems,
such as MVS, are examples of multiuser operating systems.
• Batch Processing
Types of Operating Systems
• Time sharing processing
– Each user is given a time slice to interact with the CPU.
– The size of the time slice will depend on the system.
– Each user is served in sequence.
• Real-time operating system (RTOS) - Real-time operating systems
are used to control machinery, scientific instruments and industrial
systems. An RTOS typically has very little user-interface capability,
and no end-user utilities, since the system will be a "sealed box"
when delivered for use.
• immediate response is needed.
– anti-missile defense system
– airplane landing control system
Uniprogramming
• Processor must wait for I/O instruction to
complete before preceding
Batch processing
• Jobs, together with input data, are fed into
the system in a batch.
• The jobs are then run one after another.
• No job can be started until previous job is
completed
Multi-tasking
• to handle 2 or more programs at the same
time from a single user ‘s perception
– CPU can only perform one task at a time,
however, it runs so fast that 2 or more jobs
seem to execute at the same time
Multi-programming
• 2 or more programs store in the main
memory at the same time
• when one job reeds to wait (e.g. I/O
operation), CPU switch to another job to
execute
• when the first job finishes waiting, CPU will
get back the first job to execute
Parallel Processing
• use 2 or more CPUs to handle jobs
• computer networking
without multiprocessing
with multiprocessing
Job 4
Job 3
Job 4
time
Job 3
Job 1
CPU 1
Job 2
CPU 2
time
Job 2
Job 1
CPU 1
Common Operating system
stand-alone operating systems or single user
operating systems
•
DOS - It is a single user operating system used
in microcomputers. It is a command line
interface
operating
system.
Microsoft
Corporation developed it for IBM 8086
microprocessor computers. It was the most
popular operating system in microcomputers
before the Windows.
•
Mac OS - developed by Apple Corporation in
1984 for Macintosh. This operating system
provides the GUI. It was one of first operating
system that introduced the GUI.
•
Microsoft Windows introduced by Microsoft. It is
most used and powerful GUI operating system.
Network Operating System
A network operating system typically
resides on a server and controls the
devices or computers connected to the
network.
•
•
•
•
•
Windows NT Server
Windows 2000 Server
UNIX
Solaris
Novell’s Netware
Embedded Operating System
Different special electronic devices (or handheld
computers) are also controlled by the operating systems
that are stored into a ROM chip..
i) Windows CE
designed for the use in wireless communication devices,
smaller computer such as handheld computer, in-vehicle
devices etc. Windows CE interface is similar to that of
Windows operating system. This operating system also
supports multitasking, Internet access, e-mails etc.
Many application programs such as Microsoft Word,
Microsoft Excel etc. that are developed for this operating
system can be run with Windows CE.
ii) Pocket PC 2002
developed by Microsoft and is used on a specific type of
handheld computer called the pocket PC. It is similar to
Windows XP operating system and is used to access
Internet, listen to music, and watch a video and to create
word processing and spreadsheet documents etc.
Iii)Palm operating system
Designed for PDA
• So next time when you start your
computer and work on it , do not forget to
appreciate the invisible performer….
• Enjoy !!!
• Thank you!!!