Interview Questions.

Question 1. What Is A Non Re­entrant Code?

Answer :

Re entrant code is code which does no longer rely on being done without interruption earlier than crowning glory. Reentrant code can be used by more than one, simultaneous responsibilities. Reentrant code normally does no longer get entry to global records. Variables within a reentrant function are allotted at the stack, so every instance of the function has its own private data. Non­reentrant code, for use adequately through a couple of approaches, ought to have get entry to managed via a few synchronization approach inclusive of a semaphore.

Question 2. How Is Rtos Different From Other Os?

Answer :

A RTOS offers services that allow obligations to be carried out inside predictable timing constraints.

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Question 3. Is Unix A Multitasking Or Multiprocessing Operating System? Whats The Difference Between The Two?

Answer :

unix is a multitasking operating gadget, multiprocessing approach it may run on a couple of processors, the multiproceesing os coordinates with multiple processors walking in parallel.

Question 4. What Is A Core Dump?

Answer :

A middle unload is the recorded country of the working reminiscence of a laptop program at a specific time, typically when this system has terminated abnormally consists of this system counter and stack pointer, memory control information, and other processor and running device flags and facts a fatal blunders normally triggers the middle unload, regularly buffer overflows, in which a programmer allocates too little memory for incoming or computed data, or get right of entry to to null guidelines, a not unusual coding errors whilst an unassigned reminiscence reference variable is accessed.

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Question five. What Is Stack Overflow And Heap Overflow?

Answer :

stack overflow occurs whilst when this system attempts to get entry to reminiscence that is out of doors the place reserved for the call stack.
Call stack carries the subroutines called, the nearby variables.
Overflow happens when too many functions are referred to as,massive quantity of nearby variables are allocated.
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Question 6. Windows Also Has Multiple Processes Has Process Priorities Switches Between Multiple Process, How Rtos Is Different From That?

Answer :

RTOS has predictable timing constraints.

Question 7. How Will U Create A Process In Unix Or Our Os Ose?

Answer :

We can use thr fork machine call to create a process in UNIX and in OSE the gadget name create_process is used.

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Question 8. What Is A Flat Memory Model And A Shared Memory Model?

Answer :

In a flatmemory version the code and data section occupies unmarried address area.
In a shared version the massive reminiscence is divided into one of a kind segments and desires a qualifier to identify every section.
In a flat memory version the programmer doesnt need to replace for information and code.
Question 9. What Is Paging, Segmentation Y Do We Need It?

Answer :

Paging: Paging is a technique wherein within the OS makes available the information required as fast as feasible. It shops some pages from the aux tool to predominant reminiscence and while a prog wishes a page that is not on the primary memory it fetches it from aux reminiscence and replaces it in important memory. It uses specialized algorithms to pick which web page to replace from in foremost reminiscence.

Caching: It deals with a concept in which the statistics is temperorarily saved in a high speed reminiscence for faster access. This data is duplicated in cache and the unique statistics is saved in a few aux reminiscence. This principles brings the average access time decrease.

Segmentation: Segmentation is a memory control scheme. This is the technique used for reminiscence protection. Any accesses out of doors premitted location could bring about segmentation fault.

Virtual Memory: This approach allows non­contiguous memory to be accessed as if it had been contiguous. Same as paging.

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Question 10. Write A Code To Check Whether A Stack Grows Upwards Or Downwards?

Answer :

void checkStack()

int i=2?

int j=3?

if(&i > &j) printf("stack grown downwards")?

else printf("stack grows upwards")?

outline 2 local variables one after other and try and print the cope with

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Question 11. Why Do We Require Semaphore?

Answer :

For system synchronization, it's miles a mechanism to invoke the dozing process to end up equipped for execution. Its mechanism in which a method can wait for sources to be available.Standard example is manufacturer patron system. The producer technique creates assets and indicators the semaphore pronouncing resource is available. Consumer process ready on the semaphore gets the signal that useful resource is available.

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Question 12. Write A Small Piece Of Code Protecting A Shared Memory Variable With A Semaphore?

Answer :

int global_i?

void increment_shared_memory 

       wait(semaphore)? 

       global_i++?

      signal(semaphore)?

Operations Management Interview Questions
Question thirteen. What Are The Different Types Of Semaphores And Where They Are Used?

Answer :

Binary semaphore and counting semaphore. Binary semaphore is equal as mutex. Binary semaphore attempts to protect best one resource.
Counting semaphore is used in case of multiple useful resource.

For ex: we've 4 printers then the counting semaphore fee can be init to four. When it reaches zero, the task ready on the semaphore is suspended.

Question 14. What Are The Different Inter Process Communications?

Answer :

semaphore, mutex, message passing, shared memory, socket connections.

Question 15. What Is Present In .Bss?

Answer :

The bss phase consists of uninitialized records, and is allocated at run­time.  Until it's far written to, it remains zeroed.

Synchronized Multimedia Integration Language (SMIL) Interview Questions
Question 16. What Are The Different Segments Of A Program?

Answer :

Memory Segments: Code section

This phrase used to refer to a part of reminiscence or of an item record that includes executable pc commands. It is usually examine­handiest segment.

Data phase: This is one of the sections of a application in an item record or in memory, which includes the global variables that are initialized with the aid of the programmer. It has a set size, on account that all of the facts in this section is ready with the aid of the programmer earlier than this system is loaded. However, it isn't always study­simplest, because the values of the variables can be altered at runtime.

.Bss: This section of memory is a part of data section that includes uninitialized records (static variables). These are initialized to 0 and later assigned values in the course of runtime.

Stack section: This section of reminiscence is a unique stack which stores information approximately the active subroutines of a undertaking. It incorporates the go back cope with to be branched to after a sub­routine has finished execution. It includes nearby variables of the sub­exercises and the parameters that are handed to those sub­ routines.

Heap segment: The segment of memory that's used for dynamic reminiscence allocation is called heap. It is the obligation of the programmer to deallocate it after its use. Or as a substitute it will likely be garbage accumulated via the OS.

Question 17. What Is An Elf?

Answer :

Executable and Linking Format is a common general file layout for executables, object code, shared libraries, and center dumps.

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Question 18. What Is Priority Inversion?

Answer :

In a situation where a low precedence undertaking holds a shared aid (instance semaphore) that is required by a excessive precedence venture. This causes the execution of the excessive priority undertaking to be blocked until the low precedence venture has launched the useful resource. This situation is averted by using the OS by increasing the concern of the low­proi technique until it completes the mission and releases the sources.

Operating System Interview Questions