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Rida Sarwar Bilgrami

B.C.S (4th Semester):

Operating System:

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Presentation Of Windows

Main Memory

Processor

P1

P2

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WINDOWS 7:An Operating System is an interface b\w hardware and user, The OS control events within computer System, As a host,one of the purposes of an OS is to handle the detail of the operation of the hardware. Fundamentally we can think of the OS as that entity that manages the use of system resources by the processes.

Virtual memory

Computer resources

Processes supported by different OS environments differ in a number of ways, including the following:

1. How Processes are named.2. How processes are represented.3. How process resources are protected.4. How processes are related to each other.5. Whether threads are provided within process.

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Pn

I/O I/O

6. What mechanism are used for inter process communication and synchronization.

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Window Process Design is driven by the need to provide support for a variety of OS environments. Important characteristics of windows processes are the following:

1. Windows processes are implemented as objects.2. A process can be created as new process, or as a copy of an existing process.3. An executable process may contain one or more threads.4. Both process and thread objects have built-in synchronization capabilities.

Virtual Address Descriptors

Handle Table

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Created By: Rida Sarwar Bilgrami

Access Token

Process Object

Handle 1

Handle 2

Handle 3

. . .

Threadx

File y

Section z

Windows Process and its resources Each Process is assigned a security access token, called the process, When a use first logs on, Windows creates an access token that includes the security ID for the user, every process that is created by or runs on behalf of this user has a copy of this access token. If the process attempts to open such a handle, the security system determines whether this is permitted and therefore whether the process may change its own attributes. Process must rely on the virtual memory manager which provides a memory allocation service for the process. The process has access to a file object and to section object that defines a section of shared memory.Process and Thread Objects: A thread is a dispatch able unit of work that executes sequentially and is interruptible, so that the processor can turn to another thread. .A Windows process must contain at least one thread to execute. Each process is defined by a number of attributes and encapsulates a no. of actions, or services that it may perform. It will perform when called upon through a set of Published Interface Methods. At a time of creation of process attribute values are assigned.

Windows Process Object Attributes 1. Process ID 2. Security Descriptor 3. Base Priority 4. Default Processor Affinity 5. Quota Limits 6. Execution Time 7. I\O counters 8. V M Operation counters 9. Execution /Debugging Ports 10. Exit status

Windows Thread Object Attributes1. Thread ID2. Thread Context3. Dynamic Priority4. Base Priority5. Thread processor Affinity6. Thread Execution time7. Alert Status8. Suspension Count9. Impersonation Token10. Termination Port11. Thread Exit Status

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Ready

Transition

Threads States

RUNNABLE:

Pick To Run Switch Preemted

Block\Suspend

Unblock Resources not available

NOT RUNNABLE

Stand BY

Running

Waiting

Terminated