UGC NET COMPUTER SCIENCE SOLVED PAPERS 2014-16 - UGC NET Computer Science Paper 2 December 2015

42. Which of the following statements is false?

  • Option : B
  • Explanation :
  • Top-down parsers are LL parsers where first L stands for left - to - right scan and second L stands for a leftmost derivation.Correct
  • (000)* is a regular expression that matches only strings containing an odd number of zeroes, including the empty string.Incorrect (000)* will generate ε, 000, 000000, 000000000, ........ multiples of 3 which include odd and even strings, so this is incorrect.
  • Bottom-up parsers are in the LR family, where L stands for left - to - right scan and R stands for rightmost derivation.Correct
  • The class of context - free languages is closed under reversal. That is, if L is any context - free language, then the language LR = {wR: w∈L} is context - free.Correct
  • So, option (B) is correct.
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43. System calls are usually invoked by using :

  • Option : C
  • Explanation :
  • System calls are usually invoked by using a software interrupt.
  • Polling is the process where the computer or controlling device waits for an external device to check for its readiness or state, often with low-level hardware.
  • Privileged instruction is an instruction (usually in machine code) that can be executed only by the operating system in a specific mode.
  • In direct jump, the target address (i.e. its relative offset value) is encoded into the jump instruction itself.
  • So, option (C) is correct.
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44. The __________ transfers the executable image of a C++ program from hard disk to main memory.

  • Option : D
  • Explanation :
  • The loader transfers the executable image of a C++ program from hard disk to main memory.
  • Debugger is a computer program that is used to test and debug other programs(target program).
  • Compiler Compiler is a software which converts a program written in high level language (Source Language) to low level language (Object/Target/Machine Language).
  • Linker takes object files, links them with each other and with any library files that you specify, and produces an executable output file.
  • So, option (D) is correct.
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