Common Operating System (OS) Interview Preparation Guide

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☛ 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.

☛ Network re-director/ Server
☛ Cache manager.
☛ File systems
☛ Network driver
☛ Device driver

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

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

C2 level security.

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

It does not have the features like:
☛ Ability to support multiple processors
☛ Virtual storage
☛ Source level debugging

☛ Ready
☛ Standby
☛ Running
☛ Waiting
☛ Transition
☛ Terminated

It is a fault tolerance disk driver for Windows NT.

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

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

It is the transfer of sufficient amount of the state of process from one machine to the target machine.

☛ Swapping
☛ Interactive user request
☛ Timing
☛ Parent process request

When the OS at the explicit request of another process creates a process, this action is called process spawning.

It does not have the features like:
☛ Ability to support multiple processors
☛ Virtual storage
☛ Source level debugging

No Windows NT is not so, because its not implemented in object oriented language and the data structures reside within one executive component and are not represented as objects and it does not support object oriented capabilities.

Encapsulation, Object class and instance.

To achieve maximum efficiency and reliability a mode of operation known as symmetric multiprocessing is used. In essence, with SMP any process or threads can be assigned to any processor.

☛ Hardware abstraction layer
☛ Kernel
☛ Subsystems
☛ System Services.

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

Page swapping or page replacements are called page cannibalizing.

With demand paging, a page is brought into memory only when a location on that page is actually referenced during execution. With pre-paging, pages other than the one demanded by a page fault are brought in. The selection of such pages is done based on common access patterns, especially for secondary memory devices.

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.

Placement algorithms determine where in available real-memory to load a program. Common methods are first-fit, next-fit, best-fit. Replacement algorithms are used when memory is full, and one process (or part of a process) needs to be swapped out to accommodate a new program. The replacement algorithm determines which are the partitions to be swapped out.

If a process in a monitor signal and no task is waiting on the condition variable, the signal is lost. So this allows easier program design. Whereas in semaphores, every operation affects the value of the semaphore, so the wait and signal operations should be perfectly balanced in the program.