Aptitude [Sasken Placement]: Sample Questions 4 - 5 of 35

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Question 4

Aptitude
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Short Answer▾

When deadlock occurs?

Explanation

  • In an operating system, a deadlock is a situation which occurs when a process or thread enters a waiting state because a resource requested is being held by another waiting process, which in turn is waiting for another resource held by another waiting process.
  • Conditions for deadlock to occur are given below.
  1. Mutual Exclusion: At least one unsharable resource - processes claim exclusive control of resources they need
  2. Hold and Wait: Process holds one resource while waiting for another
  3. No Pre-emption: Resources only released voluntarily - no interruption possible (i.e.. cannot be forcefully withdrawn by another process)
  4. Circular Wait: Circular chain of processes - each waiting for a resource held by another

Question 5

Aptitude
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Short Answer▾

What is flow control and where it is done?

Explanation

Flow control is the management of data flow between computers or devices or between nodes in a network so that the data can be handled at an efficient pace. Too much data arriving before a device can handle it causes data overflow, meaning the data is either lost or must be retransmitted. For serial data transmission locally or in a network, Xon / Xprotocol can be used. For modem connections, either CTS/RTS (Clear to Send/Ready to Send) commands can be used to control data flow.

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