## CS 1401, Quiz #5, Solutions

**Date:** Tuesday, February 20, 2007

**Name:** ____________________________________________________________

**Class section** (9:00 am or 10:30 am): _______________________________
1. For each of the following topics, write "yes" or "no" depending
on whether this topic is covered in Chapter 5, the chapter that you
were supposed to read before the class:

while loops *yes*

2-dimensional arrays *no*

for loops *yes*

user-defined methods *no*

2. Draw truth tables for "and" and "or" and use these truth tables
to find the truth value of the statement
((3 > 2) || (2 > 3)) && (2 + 2 == 4).

Solution:
Let us denote true by T and false by F.
---------------- ----------------
| A | B | A && B | | A | B | A || B |
---------------- ----------------
| T | T | T | | T | T | T |
---------------- ----------------
| T | F | F | | T | F | T |
---------------- ----------------
| F | T | F | | F | T | T |
---------------- ----------------
| F | F | F | | F | F | F |
---------------- ----------------
Here, 3 > 2 is T, 2 > 3 is F, so (3 > 2) || (2 > 3) is T || F, which is
T.
Since 2 + 2 == 4 is T, the whole expression
((3 > 2) || (2 > 3)) && (2 + 2 == 4) is T && T, which is T (true).

3. Write down a statement that, given three real numbers *a*,
*b*, and *x*, assigns, to a Boolean variable *in*:
- the value
*true* if *x* is within the closed interval
[*a*, *b*] (i.e., if a <= x <= b) and
- value
*false* otherwise.

Solution:
if (a <= x && x <= b)
{in = true;}
else
{in = false;}