1. What is the Translation Lookaside Buffer (TLB)?

In a cached system, the base addresses of the last few referenced pages is maintained in registers called the TLB that aids in faster lookup. TLB contains those page-table entries that have been most recently used. Normally, each virtual memory reference causes 2 physical memory accesses-- one to fetch appropriate page-table entry, and one to fetch the desired data. Using TLB in-between, this is reduced to just one physical memory access in cases of TLB-hit.

2. What are the reasons for process suspension?

•  swapping
•  interactive user request
•  timing
•  parent process request

3. What are DDks? Name an operating system that includes this feature.

DDks are device driver kits, which are equivalent to SDKs for writing device drivers. Windows NT includes DDks.

4. In loading programs into memory, what is the difference between load-time dynamic linking and run-time dynamic linking?

For load-time dynamic linking : Load module to be loaded is read into memory. Any reference to a target external module causes that module to be loaded and the references are updated to a relative address from the start base address of the application module.

With run-time dynamic loading : Some of the linking is postponed until actual reference during execution. Then the correct module is loaded and linked.

5. What is the resident set and working set of a process?

Resident set is that portion of the process image that is actually in real-memory at a particular instant. Working set is that subset of resident set that is actually needed for execution. (Relate this to the variable-window size method for swapping techniques.)

6. List the Coffman's conditions that lead to a deadlock.

•  Mutual Exclusion : Only one process may use a critical resource at a time.
•  Hold & Wait : A process may be allocated some resources while waiting for others.
•  No Pre-emption : No resource can be forcible removed from a process holding it.
•  Circular Wait : A closed chain of processes exist such that each process holds at least one resource needed by another process in the chain.

7. What is mutant?

In Windows NT a mutant provides kernel mode or user mode mutual exclusion with the notion of ownership.

8. What is Executive in Windows NT?

In Windows NT, executive refers to the operating system code that runs in kernel mode.

9. What are the key object oriented concepts used by Windows NT?

•  Encapsulation
•  Object class and instance

10. What are rings in Windows NT?

Windows NT uses protection mechanism called rings provides by the process to implement separation between the user mode and kernel mode.

11. What are the typical elements of a process image?

User data : Modifiable part of user space. May include program data, user stack area, and programs that may be modified.

User program : The instructions to be executed.

System Stack : Each process has one or more LIFO stacks associated with it. Used to store parameters and calling addresses for procedure and system calls.

Process control Block (PCB) : Info needed by the OS to control processes.

12. What is a drawback of MVT?

It does not have the features like

•  ability to support multiple processors
•  virtual storage
•  source level debugging

13. What is an idle thread?

The special thread a dispatcher will execute when no ready thread is found.

14. What has triggered the need for multitasking in PCs?

• Increased speed and memory capacity of microprocessors together with the support fir virtual memory and
• Growth of client server computing

15. What are the sub-components of I/O manager in Windows NT?

•  Network redirector/ Server
•  Cache manager
•  File systems
•  Network driver
•  Device driver

16. What are short-, long- and medium-term scheduling?

Long term scheduler determines which programs are admitted to the system for processing. It controls the degree of multiprogramming. Once admitted, a job becomes a process.

Medium term scheduling is part of the swapping function. This relates to processes that are in a blocked or suspended state. They are swapped out of real-memory until they are ready to execute. The swapping-in decision is based on memory-management criteria.

Short term scheduler, also know as a dispatcher executes most frequently, and makes the finest-grained decision of which process should execute next. This scheduler is invoked whenever an event occurs. It may lead to interruption of one process by preemption.

17. Paging a memory management function, while multiprogramming a processor management function, are the two interdependent?

Yes

18. List out some reasons for process termination

•  Normal completion
•  Time limit exceeded
•  Memory unavailable
•  Bounds violation
•  Protection error
•  Arithmetic error
•  Time overrun
•  I/O failure
•  Invalid instruction
•  Privileged instruction
•  Data misuse
•  Operator or OS intervention
•  Parent termination