2’s complement help

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    • #3797
      ethicalhack3r
      Participant

      Hello,
      I had an exam this morning which had the following question:

      What is the largest positive value that can be represented using a 16-bit 2’s complement representation?

      My answer was 32766

      Im sure its wrong tho, any one know the real answer?

    • #24271
      hayabusa
      Participant

      Been a while since I’ve done this.  I think you’re one shy, and the answer is 32767.

      16-bit would be 1000000000000000, and flipping the bits would yield 0111111111111111, which is equal to 32767 decimal.

      To support my thinking, I found the following:

      “For instance, a 16-bit word can represent signed integers in the range −32 768 to + 32 767.”

      which I took from:

      http://openlearn.open.ac.uk/mod/resource/view.php?id=175771

      HTH.

      (edit – please excuse me if I’m incorrect, and someone tell us otherwise…  been a LONG time since I’d done these, too)

    • #24272
      ethicalhack3r
      Participant

      I think your right because 0 is a positive number and I completely forgot about it.

      Thanks for the help!  🙂

    • #24273
      jason
      Participant

      What was the subject matter of the test, out of curiosity?

    • #24274
      ethicalhack3r
      Participant

      Computer System Fundamentals

      The whole module was based on the following book:
      Fundamentals of Computer Architecture – Mark Burrell (2004)

    • #24275
      RoleReversal
      Participant

      Ethicalhack3r,

      @ethicalhack3r wrote:

      The whole module was based on the following book:
      Fundamentals of Computer Architecture – Mark Burrell (2004)

      Just out of interest, was Mark Burrell also one of the module lecturers?
      I remember some sleep-inducing lectures from him 😀

      Andrew

    • #24276
      ethicalhack3r
      Participant

      He wasnt one of my lecturers but he used to lecture at Northumbria, think he left a couple of years ago maybe?!

      I think its the logic gates that get me nodding off…

    • #24277
      RoleReversal
      Participant

      Must have left after my days then, tbh think the whole module got me sleeping.

      Wish I’d paid more attention now I’m playing with shellcode, turns out the low-level stuff is still relevant. Who’d of thought the lecturers would have a better understanding of the industry than the students? 🙂

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