CS 10: Introduction to Computer Programming

In-Class Examination 1

Closed-Book, 50 minutes, Fall 1997

General Instructions

Before you answer any questions, write your name and perm number on your answer booklet.
Read each question carefully.
Make sure that you clearly understand a question before answering it.
Please put your answer to each question on its own page in your blue-book.
You may wish to work out an answer on scratch paper before writing it on your answer page; answers that are difficult to read may lose points for that reason.

Question	Value
1	25
2	25
3	25
4	25
Total	100

1. What is the value of variables i, j, and k after the statements below have been executed?

int i = 7, j = i + 1, k = j*j;

j -= j;
k += --i + 5;
i *= i % 4;

Solution: j = 0, k = 75, i = 12.

2. Write java statement[s] that assign 7 to int variable j, if the value of int variable i is evenly divisible by 2 and 3 and is evenly divisible by neither 5 nor 7, and assigns -7 to int variable j otherwise. Do not use boolean operators.

Solution:

j = -7;

if (i % 6 == 0)

if (i % 5 != 0)

if (i % 7 != 0)

j = 7;

3. Convert the following code fragment to an equivalent one that uses for statements in place of the while statements. If this cannot be done, explain why.

int i = 1, limit = 8, n;

double x = i, term, e2x;

        System.out.println("Begin computation of various values of e");
        while (i <= 10) {
            n = 1;
            x *= -i;
            e2x = term = 1.0;
            System.out.println(i + ": x = " + x);

            while (n <= limit) {
                term *= x/n;
                e2x += term;
                System.out.println("    " + n + ": term = " + term + ", e2x = " + e2x );
                n++;
            }
            i++;
            System.out.println("    End computation of e to " + x);
        }
        System.out.println("End computation of various values of e");

Solution:

int i, limit = 8, n;
double x = 1.0, term, e2x;

        System.out.println("Begin computation of various values of e");
        for (i = 1; i <= 10; i++) {
            x *= -i;
            e2x = term = 1.0;
            System.out.println(i + ": x = " + x);

            for (n = 1; n <= limit; n++) {
                term *= x/n;
                e2x += term;
                System.out.println("    " + n + ": term = " + term + ", e2x = " + e2x );
            }
            System.out.println("    End computation of e to " + x);
        }
        System.out.println("End computation of various values of e");

4. Complete the following skeletal applet so that it produces a "bull's eye". The bull's eye is centered on pixel (150, 150). The inner circle is of radius 40 pixels, and is black. The middle ring is white and is 40 pixels wide. The outer ring is black and is 40 pixels wide.

import java.awt.*;

import java.applet.*;

public class bullsEye extends Applet {

public void paint( Graphics g ) {

}
}

Solution:

import java.awt.*;
import java.applet.*;

public class bullsEye extends Applet {

    public void paint(Graphics g) {
        g.fillOval(30, 30, 240, 240);
        g.setColor(Color.white);
        g.fillOval(70, 70, 160, 160);
        g.setColor(Color.black);
        g.fillOval(110, 110, 80, 80);
    }
}