History Description of Windows Architecture Layered Architecture Portability System Components Processes & Threads Kernel Scheduling Object Manager Virtual Memory Management File System Memory Management

2. Operating System
Topic
Windows 7 Architecture
Presented By
Daniyal Khan
Haris Mobeen Ahmed
Hammad Jameel Syed
Adeel Awan
Nasir Ali

3. History
Windows 7 is a personal computer operating
system developed by Microsoft. It is a part of
the Windows NT family of operating
systems. Windows 7 was released on July
22, 2009, and became generally available on
October 22, 2009.

4. Description of Windows
Architecture

5. Layered Architecture
• Kernel layer runs in protected mode and
provides access to the CPU by supporting
threads, interrupts, and traps.
• Executive runs in protected mode above the
Kernel layer and, provides the basic system
services.
• On top of the executive, environmental
subsystems operate in user mode providing
different OS APIs

6. Portability
• Windows 7 can be moved from on
hardware platform to another with
relatively few changes
• Written in C and C++
• Platform-dependent code is isolated in a
dynamic link library (DLL) called the
“hardware abstraction layer” (HAL)

7. System Components
„Four main responsibilities:
1. Thread scheduling
2. Interrupt and exception handling
3. Low-level processor synchronization
4. Recovery after a power failure

8. System Components
Kernel is object-oriented, uses two sets of objects
1. Dispatcher objects control dispatching and
synchronization (events, mutants, murexes,
semaphores, threads and timers)
2. Control objects (asynchronous procedure calls,
interrupts, power notify, process and profile
objects)

9. Processes & Threads
 „The process has a virtual memory address
space, information (such as a base priority), and
an affinity for one or more processors.
 Threads are the unit of execution scheduled by
the kernel’s dispatcher.
 Each thread has its own state, including a
priority, processor affinity, and accounting
information.
 A thread can be one of six states: ready, standby,
running, waiting, transition, and terminated.

10. Kernel Scheduling
„Characteristics of Windows 7’s priority strategy:
 Gives very good response times to interactive
threads that are using the mouse and windows
 Enables I/O-bound threads to keep the I/O
devices busy
 Compute-bound threads soak up the spare CPU
cycles in the background

11. Object Manager
 Windows 7 uses objects for all its services and
entities; the object manager supervises the use of all
the objects
1. Generates an object handle used by applications to
refer to objects
2. Checks security
3. Keeps track of which processes are using each
object „
 Objects are manipulated by a standard set of
methods, namely create, open, close, delete, query-
name, parse and security.

12. Virtual Memory
Management
 The design of the VM manager assumes that the
underlying hardware supports virtual to physical
mapping, a paging mechanism, transparent
cache coherence on multiprocessor systems, and
virtual address aliasing.
 The VM manager in Windows uses a page-based
management scheme with a page size of 4 KB for
both x86 and AMD64.

13. File System
 The fundamental structure of the Windows 7 file system
(NTFS) is a volume
1. Created by the Windows disk administrator utility
2. Based on a logical disk partition
3. May occupy a portions of a disk, an entire disk, or span
across several disks „
 All metadata, such as information about the volume, is stored
in a regular file „NTFS uses clusters as the underlying unit of
disk allocation
1. A cluster is a number of disk sectors that is a power of two
2. Because the cluster size is smaller than for the older 16-bit
FAT file system, the amount of internal fragmentation is
reduced

14. Memory Management
 Virtual memory:
1. Virtual Allot reserves or commits virtual memory
2. Virtual Free DE commits or releases the memory
3. These functions enable the application to
determine the virtual address at which the memory
is allocated
 An application can use memory by memory mapping
a file into its address space
1. Multistage process.
2. Two processes share memory by mapping the same
file into their virtual memory.

15. Memory Management
 A heap in the Win32 environment is a region of reserved
address space.
1. A Win 32 process is created with a 1 MB default heap.
2. Access is synchronized to protect the heap’s space
allocation data structures from damage by concurrent
updates by multiple threads.
 Because functions that rely on global or static data
typically fail to work properly in a multithreaded
environment, the thread-local storage mechanism
allocates global storage on a per-thread basis.
1. The mechanism provides both dynamic and static
methods of creating thread-local storage