Introduction to Computer Science:
Quiz 2
    Sewickley Academy, 2000-2001

See Course Home Page.  Also, see the Solutions to Quiz 2.

    SHOW YOUR WORK  and  WRITE NEATLY !!!

1.  Perform the following conversions between bases:

a.  Convert 0101 00102 to decimal:
 
 

b.  Convert 0011 1011 to hexadecimal:
 
 

c.  Convert 3A16 to decimal:
 
 

d.  Convert 19310 to binary:
 
 

e.  Convert 0x19FE to binary:
(hint:  recall that "0x" indicates that the number is in hexadecimal)
 
 
 

2.  People are generally more comfortable using decimal rather than binary numbers, yet we often use binary numbers in computer science.  There is a good reason for this, however.  Very briefly explain why.
 
 
 
 
 
 

3.  Very briefly explain the key shortcoming of the 7-bit ASCII code which the 16-bit Unicode attempts to remedy.
 
 
 
 
 
 
 
 

4.  Recalling that the ASCII code for A is 6510, B is 6610, C is 6710, etc,  list all the letters between A and G (inclusive) whose ASCII code, when written in binary, has even parity.  Be sure to show your work.
 
 
 
 
 

5.  Write a circuit diagram for a 3-bit odd parity tester.  This circuit takes 3 bits of input, and has 1 bit of output, the output being true precisely when the 3 input bits have odd parity.  Be sure to label each gate.
 
 
 
 
 

6.  An Error Correcting Code where every value has a Hamming Distance of at least 5 from every other value can detect 4-bit errors and correct 2-bit errors.  Very briefly explain.  (Hint:  Recall that the Hamming Distance between two binary numbers is the number of bits which must flip to convert one number into the other.)
 
 
 
 
 

7.  True or False:

a) It is easier to convert between binary and hexadecimal numbers than to convert between binary and decimal numbers (and this is why computer scientists use hexadecimal as a shorthand for binary numbers).

b) A 16-digit binary number can always be represented with a 3-digit hexadecimal number.

c)  Every binary number has either even or odd parity.

d)  A better name for a "clock" in a digital circuit might be a "strobe" because its primary purpose is not to tell the time of day, like a wall clock, but rather to turn on and off repeatedly like a strobe light.
 
 

See Course Home Page.