Os Ainterview Questions and Answers

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1.| What is an operating system?|
 | An operating system is a program that acts as an intermediary between the user and the computer hardware. The purpose of an OS is to provide a convenient environment in which user can execute programs in a convenient and efficient manner. It is a resource allocator responsible for allocating system resources and a control program which controls the operation of the computer hardware. |

2.| Why paging is used? |
 | Paging is solution to external fragmentation problem which is to permit the logical address space of a process to be noncontiguous, thus allowing a process to be allocating physical memory wherever the latter is available.|

3.| Explain the concept of the batched operating systems?|  | In batched operating system the users gives their jobs to the operator who sorts the programs according to their requirements and executes them. This is time consuming but makes the CPU busy all the time.|

4.| What is purpose of different operating systems?|
 | The machine purpose workstation individual usability &resources utilization mainframe optimize utilization of hardware PC support complex games, business application Hand held PCs Easy interface & min. power consumption.|

5.| What is virtual memory?|
 | Virtual memory is hardware technique where the system appears to have more memory that it actually does. This is done by time-sharing, the physical memory and storage parts of the memory one disk when they are not actively being used.|

6.| What is Throughput, Turnaround time, waiting time and Response time?|  | Throughput : number of processes that complete their execution per time unit.

Turnaround time : amount of time to execute a particular process.

Waiting time : amount of time a process has been waiting in the ready queue.

Response time : amount of time it takes from when a request was submitted until the firstresponse is produced, not output (for time-sharing environment). |

7.| What are the various components of a computer system?|  | * The hardware * The operating system * The application programs * The users.|

8.| What is a Real-Time System?|
 | A real time process is a process that must respond to the eventswithin a certain time period. A real time operating system is an operating system that can run realtime processes successfully.|

9.| Explain the concept of the Distributed systems?|
 | Distributed systems work in a network. They can share the network resources,communicate with each other.|

10.| What is SCSI?|
 | SCSI - Small computer systems interface is a type of interface used for computer components such as hard drives, optical drives, scanners and tape drives. It is a competing technology to standard IDE (Integrated Drive Electronics).| 11.| What is a sector?|

 | Smallest addressable portion of a disk. |

12.| What are the different operating systems?|
 | * Batched operating systems * Multi-programmed operating systems * Timesharing operating systems * Distributed operating systems * Real-time operating systems.|

13.| What is busy waiting? |
 | The repeated execution of a loop of code while waiting for an event to occur is called busy waiting.|

14.| What are system calls?|
 | System calls provide the interface between a process and the operating system. System calls for modern Microsoft windows platforms are part of the win32 API, which is available for all the compilers written for Microsoft windows.|

15.| What are various scheduling queues?|
 | * Job queue * Ready queue * Device queue|
16.| What are java threads?|
 | Java is one of the small number of languages that support at the language level for the creation and management of threads. However, because threads are managed by the java virtual machine (JVM), not by a user-level library or kernel, it is difficult to classify Java...
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