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Process object, Access Token, Virtual Address Descriptors (VAD), Handle(s) to object(s), thread(s), zero or more
thread access token.

2. What is Process Access Token ?

Access Token of a process is nothing but a security context of the Process. Access token contains security identification
and credentials for the process.

3. what are virtual address descriptors of a process in Windows ?

VADs are data structures that the memory manager uses to keep track of the virtual addresses the process is using.

4. How user mode process executes Kernel mode functions ?

Execution mode of  user mode application changes from user mode to kernel mode when it invokes a system service call.
Execution mode to kernel mode can be changed by executing a special processor specific instruction. This special
instruction is trapped by operating system, validates the inputs, executes its internal function, changes it execution
mode to user mode and returns the value.

5. what is thread context in Windows ?

Thread context contains information related to volatile registers, thread stack and thread private storage area.
We can get thread context using function GetThreadContext. Thread context depends on processor architecture.

6. Explain priority-based scheduling mechanism built into Windows ?

7. Can you change user mode threads scheduling in Windows ?

You can change user mode threads scheduling by changing them to Fibers.

8. What are Fibers ?

Fibers are “lightweight” thread and they are implemented in user mode in Kernel32.dll not visible to Windows Kernel .

9. How do you create Windows Fibers ?

Any windows user mode thread can be converted to Fiber using ConvertThreadToFiber function. Any fiber can create
another fiber using CreateFiber function.

10. How do you schedule Fiber ?

Only way to schedule a Fiber by using SwitchToFiber function.

11. what is the relation ship between process and its threads ?

A process generally contains one or more number of threads. Each thread is having its own
execution context(volatile registers, thread stack and thread private storage area). All threads in a process
shares the process’s virtual address space and other resource handles.

12. Can a thread from a process can read or modify in another process memory ?

Yes, using file mapping object(shared memory section  ). A Process can use ReadProcessMemory and
WriteProcessMemory to write into another process memory if it have a right.  

If you find any mistakes or if you have better answer for any of the question, please leave your comments below.

References:
1. Windows Internals, 5th edition by Mark E. Russinovich, David A. Solomon and Alex Ionescu
2. MSDN online

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