Question 7 on digital from GATE (Graduate Aptitude Test in Engineering) 2012 Electronics and Communication Engineering paper.

## Q7. The output Y of a 2-bit comparator is logic 1 whenever the 2 bit input A is greater than 2 bit input B. The number of combinations for which output is logic 1 is

## (A) 4

## (B) 6

## (C) 8

## (D) 10

## Solution

Let’s write all the 16 possible combinations of A and B and count the number of times A is greater than B. Can easily see that the count is 16.

A |
B |
Out |

0 | 0 | 0 |

0 | 1 | 0 |

0 | 2 | 0 |

0 | 3 | 0 |

1 | 0 | 1 |

1 | 1 | 0 |

1 | 2 | 0 |

1 | 3 | 0 |

2 | 0 | 1 |

2 | 1 | 1 |

2 | 2 | 0 |

2 | 3 | 0 |

3 | 0 | 1 |

3 | 1 | 1 |

3 | 2 | 1 |

3 | 3 | 0 |

TOTAL |
6 |

Alternately, pick each value of A and count the number of instances when A is greater than B. The count is 0 + 1 + 2 + 3 for A = 0,1,2,3 respectively.

**Based on the above, the right choice is (B) 6**

** **

## References

[1] GATE Examination Question Papers [Previous Years] from Indian Institute of Technology, Madras http://gate.iitm.ac.in/gateqps/2012/ec.pdf

D id you like this article? Make sure that you do not miss a new article
by subscribing to RSS feed OR subscribing to e-mail newsletter.
* Note: Subscribing via e-mail entitles you to download the free e-Book on BER of BPSK/QPSK/16QAM/16PSK in AWGN.*

{ 1 comment… read it below or add one }

With havin so much written content do you ever run into any issues of plagorism or copyright violation? My blog has a

lot of unique content I’ve either authored myself or outsourced but it appears a lot of it is popping it up

all over the web without my permission. Do you know any methods to

help prevent content from being ripped off? I’d genuinely appreciate it.