CSc 12: Introduction to Computing

Sample 6 Weeks Exam

1. Which of the following were great 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 mill and store.

_____ 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. Why is it a good idea to analyze a problem in terms of use cases before designing a solution or writing code? Give at least two reasons.

4. 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 produces its perimeter.

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.

___ d) A blind hacking approach can get blind-sided by a combinatorial explosion.

(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.)