Computer Science 2500 Computer Organization Rensselaer Polytechnic Institute Spring 2009

Agenda

• Announcements
  • Upcoming talk: Richard Stallman, Thursday, January 22, 5 PM.
  • Upcoming career fair: Tuesday, January 27.
• Lecture assignment recap
• Wrapping up binary arithmetic
• Bit manipulations
  • logical operations and shifts
• Floating-point representations
• C and Unix overview

Examples

• shiftyproduct
• hello
• gcd-c
• matmult

Lecture Assignment

Due at the start of class, Tuesday, January 20.

Turn in short answers to these questions. Please turn in a hard copy (typeset or handwritten are OK). We will discuss these questions during class, so no late submissions are accepted.

The readings for next time are P&H Sections 2.1-2.3.

1. Compute the following binary 2's complement problems in 4 bits. Which answers to you trust?

    0001      0001      1001      1111
   +0101     +0111     +1111     +0101
    ----      ----      ----      ----
   
   
   

2. Compute the following binary 1's complement problems in 4 bits. Which answers do you trust?

     0001      0001      0000      1000
    +0101     +0111     +1111     +1111
     ----      ----      ----      ----
   
   
   

3. The following problems are expressed in 8 bit, hexadecimal, 2's complement. Compute the result as 16 bit 2's complement expressed in hex. Which answers do you trust?

     FF        FF        01        4c       7f       80
   + 11      + FF      + 7F      x 04     x 7f     x 80
   ----      ----      ----      ----     ----     ----
   
   

4. True or false: 0.1 (base 10) can be represented as a floating point number within the computer. Justify your answer.
5. True or false: The signed product of two signed n-bit numbers can always be correctly expressed as a signed 2n-bit number. Justify your answer.