Quiz 2 - Answers

1. How is the meaning of "=" in an assignment statement, such as x=x+1 in Visual Basic, different from the meaning of "=" in algebra?

   In Visual Basic, "=" is the assignment operator. It means that the expression on the right hand side is evaluated, and the result is stored in the variable on the left hand side. So in the statement x=x+1, the expression x+1 is evaluated (using the current value of x), and the result is stored back in x (thus changing the value of x).

   In algebra, "=" means that the two sides of the equation must be equal. There isn't any notion of changing the value of a variable as you go. So in algebra, x=x+1 is just an unsatisfiable equation.

2. What is the value of x after the following Visual Basic statements are executed?

   Dim x As Integer
   x = 10
   x = 3+x*4
   x = x-1
   

   42

3. What is the value of y after the following Visual Basic statements are executed?

   Dim y As Integer
   y = 10
   If y>5 Then
     If y>10 Then
       y = 20
     Else
       y = 5
     End if
   Else
     y = 0
   End if
   

   5

4. What is the value of x after calling the procedure Squid?

   Dim x As Integer
   
   Private Sub squid ()
     x = 0
     Call clam
     Call clam
   End sub
   
   Private Sub clam
     x = x+3
   End sub
   

   6

5. What was the timer control used for in Part 1 of Project 1?

   The timer control is used to call a procedure every second that updates the displayed time.