CSc 10: Introduction to Computing

Final Exam sample questions

 

Answer the following T or F.  Explain why or why not.  (3 each, 45 total)

See http://www.cse.lehigh.edu/~glennb/um/book/exsolnew.htm.

 

What is an advantage of value parameters?     

 

 

What are two advantages of  reference parameters?

 

 

Write a method which, given an String, converts all the ‘.’ (periods) into ‘.’ (commas) and returns the new String.    Note: do not use any library functions other than length, charAt and setCharAt.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In each of the following code fragments: a) find and explain a bug, b) fix it (by marking up the code on this sheet), and c) show your corrected version's output.

            const int Sentinel = -1;

int count=0;

float sum=0;

int score;

System.out.println("Enter scores, stopping with –1:");

while (score != Sentinel)

{ score = Input.getInt();

  count = count + 1;

  sum = sum + score;

}

System.out.println(count + " scores averaging " + sum / count);

//Assume user types in: 70 81 -1

 

 

 

 

 

 

 

 

 

 

 

static void switchEm(int x,int y)

{ int temp=x;

  x = y;

  y = temp;

}

public static void main(String args[])

{ int a=1,b=2;

       switchEm(a,b);

  System.out.println("Now " + a + " is bigger than " + b);

}

 

 

 

 

 

 

 

 

 

 

 

 

Explain why multiprogramming can improve the performance or Athroughput@ of each of the following types of systems:

a) Batch operating systems

 

 

 

 

b) Time-sharing operating systems

 

 

 

 

 

6. Consider the following snippet from the atm_oop program:

public class Account

{ public Account() {}

  public int getPIN() { return PIN; }    

  void setPIN(int pin) { PIN = pin; }

  protected int PIN; //Personal Identification Number

}

 

a) Given the above class definition, define a variable, myAccount, of this type, then assign it a PIN.

     

 

 

b) Why is the following snippet illegal?  Why is making it illegal a good idea?

      if (myAccount.PIN == 2468)

 

 

 

c) Derive another class, Savings, from class Account.  Declare a constructor for your new class which requires a PIN number.

           

 

 

d) How do classes illustrate the power of abstraction?

 

 

 

e) How does class inheritance further illustrate abstraction?

Th.. th.. th.. that's all folks!