Windows OS Architecture in Summery

Presented By :
Arachchi N.C.R. (148205J)
Dilruk G.A. (148209B)
Thursday, April 23, 2015 1

Index …
 Microsoft Windows Overview
 History
 Single-User Multitasking
 Architecture
 Operating System Organization
 User-Mode Processes
 Client/Server Model
 Threads and SMP
 Windows Objects

History
 MS-DOS/PC-DOS 1.0- 1981
 Developed for first IBM PC
 Consist of 4000 lines of assembly source code
 Ran in 8KB
 Used Intel 8086 microprocessor
 DOS 2.0- 1983
 Released with IBM PC XT
 Support Hard Disk and provided hierarchical directories
 Memory resident portion up to 24KB

History cont.…
 MS-DOS 3.0/Windows 1.0- 1984
 Introduced with IBM AT PC
 Support for new Keyboard and Hard Disk peripherals
 Memory requirement 36KB
 MS-DOS 3.1- 1984
 Support for Networking of PC’s
 MS-DOS 3.3- 1987
 Support for IBM PS/2
 Memory resident portion grown minimum of 46KB

History cont.…
 Windows 3.0- 1990
 Introduced GUI
 Support for new Keyboard and Hard Disk peripherals
 Memory requirement 36KB
 MS-DOS 3.1- 1984
 Support for Networking of PC’s
 MS-DOS 3.3- 1987
 Support for IBM PS/2
 Memory resident portion grown minimum of 46KB

History cont.…
 Windows 95- 1995
 Introduced Taskbar, Start menu, Explorer file manager
 Windows 98- 1998
 Usage of WDM (Windows Driver Model)
 USB Support
 Windows 2000- 2000
 Plug and Play improvements

History cont.…
Windows XP-2001 Windows Vista-
2006
Windows 7-2009 Windows 8-2012Thursday, April 23, 2015 7

Single-User Multitasking
The operating system is designed mainly with a single user in
mind, but it can deal with many applications running at the same
time.
What happens if a user wishes to create a drawing and paste it
into a word processing document without multitasking??
Potentials
 Increased speed and memory capacity of microprocessors.
 Growth of client/server computing
1. Open the drawing program.
2. Create the drawing and save it in a file or on a temporary
clipboard.
3. Close the drawing program.
4. Open the word processing program.
5. Insert the drawing in the correct location

Architecture
HAL
Set of routines that
give a program
access to the
hardware
resources
HAL makes each
machine hardware
look same to the
kernel
Delivers the
support needed for
symmetric multi
processing (SMP)

Architecture cont.…
Kernel
Contains most
used and
fundamental
component.
Manages
• Thread
scheduling
• Process
switching
• Exception and
interrupt
handling
• Multiprocessor
synchronization
Only part that is
not preemptive andThursday, April 23, 2015 10

Architecture cont....
Device Drivers
Include file system
and hardware
drivers
Translate user I/O
function calls to
hardware specific
requests.

Windowing and
graphics system
Handles GUI
functions such as
window component
management,
drawing, etc..

Executive
Contains the base
OS services such
as
• Memory mgmt.
• Process and
thread mgmt.
• Security
• I/O
• Inter process
communication

I/O Manager
Implements all the
Windows I/O APIs
Enforces security
and naming for
devices and file
systems

File System Cache
Improves the
performance by
keeping recently
referenced disk
data and holding
updates for short
time

Object Manager
Creates, manages
and deletes
executive objects,
processes, threads
and
synchronization
objects
Create object
handlers which
consist of access
control information
and a pointer to
the object

Plug and Play
manager
Determines which
drivers are
required to support
a particular device
and load them

Power Manager
Coordinates the
power among
devices and
reduce the power
consumption by
putting the
processor to sleep
on idle

Security reference
monitor
Manages the
access and the
audit logs through
out the system

Virtual Memory
Manager
Maps the virtual
address in the
process’s address
space to physical
addresses

Process / Thread
Manager
Manage processes
and threads

Configuration
manager
Responsible
manage the
system registry
which contains the
system and user
settings

Local procedure
call
Manage the
communication
between executive
subsystems

User Mode processes
System Support
Processes
Include the
services not
provided as part of
the kernel
• Logon process
• Session
manager
• Local Security
authentication
server

Service Processes
Other windows
services such as
event logger,
spooler
User Mode processes

User Applications
Can be a
• Win32
• Posix
• OS/2
• Windows 3.1
• MS-DOS
application
User Mode processes

Environment
Subsystems
Expose the
windows services
to user
applications.
Responsible to
convert user
application calls to
windows calls
User Mode processes

Client/Server Model
 Each environment and a execute service subsystem is
implemented as one or more processes
 Each process waits for a request from a client for one of its
services
 Client requests a service by sending a message
 Server performs the requested operation and returns the
result
 Advantages
 Simplifies the Executive
 Improves Reliability
 Provides suitable base for distributed computing

Threads and SMP
 OS routines can run on any available processor
 Windows supports multiple threads execution within a single
process
 Server processes may use multiple threads to process
request from more than one client simultaneously
 Windows provides mechanisms for sharing data resources
between processes and flexible interprocess communication
capabilities

Windows Objects
 The approach of object-oriented design facilitates the sharing
of resources and data among processes and the protection of
resources from unauthorized access
 Encapsulation
 Object class and instance
 Inheritance
 Polymorphism
 Object may be either named or unnamed
 Eg. of objects managed by kernel (two categories)
1. Control objetcs
2. Dispatcher objects

Continue …
 Windows Threads
 Process & Thread Objects
 Multithreading
 Thread States
 Symmetric Multiprocessing
 Windows Memory Management
 Virtual Address Map
 Paging
 Windows Scheduling
 Process & Thread Priorities
 Multiprocessor Scheduling

Windows Process & Thread
Objects
 Windows process are implemented as objects
 Executable process may contain one or more threads
 Each process is assigned a security access token

Windows Process & Thread
Objects

Multithreading
 Threads in different process can execute
concurrently
 Moreover, multiple threads within the same
process execute simultaneously in different
processors
 Threads within same process can exchange
information through their common address space
 Ex : In server application each client can have a
separate thread to service

Thread States

Symmetric Multiprocessing
 Threads of any process can run on any processor
 Windows microkernel assigns a ready thread to
the next available processor in case of absence
of affinity restrictions
 Two Affinity policies
 Soft affinity
 Hard affinity

Windows Memory Management
 Each process on 32-bit Microsoft Windows has its
own virtual address space that enables
addressing up to 4 gigabytes of memory
 Memory manager controls memory allocation and
how paging is performed
 Only some parts of the program and data that are
currently in active use need to be held in physical
RAM and other parts are in a swap file

Virtual Address Space
 Virtual address space for a
process is the set of virtual
memory addresses that
process can use
 The virtual address space
for 32-bit Windows is 4
gigabytes (GB) in size and
divided into two partitions:
one for use by the process
and the other reserved for
use by the system

Windows Paging
 Page sizes are ranging from 4Kb to 64Kb for different
platforms
 Two-level hierarchical memory map
 Page directory table
• Page directory entries (PDEs) point to page table
• One page directory table per process
• Location in page directory register
 Page table
• Page table entries (PTEs) point to page frames
 TLB (translation look aside buffer) accelerates address
translation
 Windows use local page replacementThursday, April 23, 2015 39

Virtual Address Translation

Windows Scheduling
 Mainly consider responsiveness in highly
interactive environment.
 Preemptive scheduling
 Priority levels
 Round-robin scheduling Algorithms

Process & Thread Priorities
 Two priority classes, real time and variable
 Each consist of 16 levels
 Threads needed immediate attention is in the real
time class, those have precedence over others
 Lower priority thread will preemptive when higher
one is ready
 Real-time class priorities are fixed while variable
class can up or downThursday, April 23, 2015 42

Multiprocessor Scheduling
 In a multiprocessor system with N processors
 The (N -1) highest priority thread are always active
 And running on (N -1) extra processors
 The Remaining lower priority threads share the
single remaining processor

Windows OS Architecture in Summery

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