CSc 10: Introduction to Computing
6 Weeks
Exam: Fall 1996 (modified for Fall 2001, using Java)
1.
Which of the following were Agreat ideas@ of Babbage=s
Analytical Engine that anticipated modern computers? Write a short explanation for each one, explaining why or
why not.
_____
It was a general purpose device.
_____
It was compact.
_____
It had a separate Amill@ and Astore@.
_____
It was electro-mechanical.
_____
It had a branch instruction.
2.
Below is a Knobby=s World program that adds 2 + 3.
//Knobby
adder program, by Robert Barnes and Glenn Blank
//Add
2+3 as two strings of marks: XX XXX => XXXXX
define
right as
{
//Turn Knobby's to the right
left left left
}
define
getAMark as
{
//read a mark ('X') from next corner to the right
right move read
}
define
goToBlank as
{
//go to blank past first two marks
move move
}
define
fillItIn as
{
//put a mark in blank between strings of marks
write
}
define
fillBlank as
{
//get a mark and put it in the space between strings of marks
getAMark goToBlank fillItIn
}
define
goToEnd as
{
//go the end of the second string of three marks
move move move move
}
define
getABlank as
{
//read a blank (empty corner) and turn around
read left left
}
define
erase as
{
//erase a mark (with a blank)
move write
}
define
eraseEnd as
{
//erase mark at the end of concatenated string of marks
goToEnd getABlank erase
}
define
goHome as
{
//go back to starting position
move
move move move
move move right
}
define
main as
{
//2+3 (XX XXX) == 5 (XXXXX)
fillBlank //put
a mark between the XX and the XXX
eraseEnd //erase
the mark at the end of the XXX
goHome //tada!
}
A)
What problem solving strategy did I probably use to design my solution? Why do you think so?
B)
What problem solving strategy would you use to write a Knobby program that adds
1+2? Why?
C)
Modify the Knobby program above so that it adds 1+2. Comment your code!
D)
In what way could this program be made more general? What construct of the Knobby=s
World programming language might you use to achieve this generality?
3.
Write a Java definition for pi (about 3.1416). What does this example illustrate about invariants? How
can we avoid writing this definition in Java (i.e., using code that already
exists somewhere)?
4.
Suppose you want to use the method Input.getInt() in a Java program.
a)
Write the code needed to get the Java compiler to recognize this method.
b)
What will the Java compiler do with the information supplied by the above code?
c)
When will the Java linker combine this code with your program?
5. What would the following Java expression
do? Show partial results, for
example: (15)
1 + 3 - 2
4
2
a) 2 + 7 % 3 b) sqrt(pow(3,2)) / -2 c) -3.1 * 5 % 2 + 7
6.
Given the following class interface:
class Circle
{ public Circle(double radius); //create a Circle with radius in inches
public double perimeter(); //computes perimeter in inches
public double area(); //computes
area of circle in inches
private double _radius; //radius is half diameter, in inches
}; //Circle
a)
Write a snippet of Java code that creates a Circle object, c, whose radius is 2 inches,
then displays its area on the monitor.
b)
What would happen if you tried to write a snippet of code that displayed the _radius of c? Why?
Are the following statements true or false? Explain why or why not.
___ a) Java operators can mean
different things depending on the types of their operands.
____b) Java comments cannot contain any Knobby=s World code.
___ c) Compiled code runs faster than equivalent interpreted code.
(See end of review questions at end of each chapter in the book for more of these questions.
Answers supplied in http://www.cse.lehigh.edu/~glennb/um/book/exsolnew.htm.)