## CS 1401, Quiz #1

**Date:** Thursday, January 20, 2005

**Name:**
______________________________________________________________________

**Last 4 digits of UTEP ID #:**(it is OK if you do not remember it):
______________________________________________________________________
1. Explain why the invention of variables was a good
idea. (*Hint:* how were formulas described before that?) When
were they invented? By whom?

Answer:
Variables were invented by Francois Viete (a.k.a. Francisco Vieta) in
1520. Variables enable to make descriptions of algorithms much shorter
and easier to understand, e.g., "to compute the area of the rectangle,
multiply its first side by its second side" is much more difficult to
write and to understand than A=s1*s2.

2. Describe, step by step, an algorithm that, given three
real numbers *a*, *b*, and *c*,
returns the values *x* for which *a*x+b=c*.
Answer:
Let us first move b to the other side of the equation, we get
a*x=c-b. This leads to the following algorithm:
* First check whether a = 0.
* If a =/= 0, then compute and return the value x = (c-b)/a
* If a = 0, then check whether b = c.
* If b = c, then every real number x is a solution
* If b =/= c, then the original equation has no solutions.

3. Explain which of the following five
expressions are correct names for
Java variables, and if not, why:

viete
It is a correct name, because it is a sequence of characters and/or
digits starting with a character
1520
Incorrect: starts with a digit, should start with a letter
francois_viete
Correct: underscore is allowed
francois-viete
Incorrect: - is not allowed; the only two symbols that are not
letters or digits that are allowed in a Java name are underscore and $
francois viete
Incorrect: blank space is not allowed

4. In Java, strings are described by double quotes. For example, the
text *Java* is described as follows:
"Java"

Describe, in Java, the two strings that contain
the following two texts:
Francois Viete
"Francois Viete"
At a conference SCAN'04, Viete said: "I invented variables."
"At a conference SCAN'04, Viete said: \"I invented variables.\""