If Statements (CS) Visual Basic

Question

1. 

intX = 129

intY = 200

intCount = 1

 

If (intX > 120 And intY < 30) Then

intCount = intCount + 1

Else

intCount = -1

End If

 

intCount = ?????

 

Can someone please explain this to me?

Answer 1

This code snippet is intended to be a "tricky" test question to determine whether you comprehend the precedence rules for "And" in a compound expression.  That is, does the statement

   If (intX > 120 And intY < 30) Then

mean

   If ( (intX > 120) And (intY < 30) ) Then

or does it mean

   If (intX > (120 And intY) < 30) Then

 

Note that the "And," as in "(120 And intY)". is listed as a Logical and Bitwise Operator (for Conjunction) in:

   https://msdn.microsoft.com/en-us/library/fw84t893(VS.100).aspx

Answer 2

Ok, so this program fragment can be described as:

1. Assign (put) some integer numbers into variables.

2. Check a condition by looking at what's in those variables

    If the condition is TRUE, execute the THEN statement

    If the condition is FALSE, execute the ELSE statement

 

So let's check the condition (intX > 120 And intY < 30). 

To do that we substitute the values for the variables intX and intY which were set above.

 

Substituting into the condition:

 

If ( intX > 120 And intY < 30)

becomes

If ( 129 > 120 And 200 < 30 )

 

Since the keyword "And" is used, for the condition to be true, BOTH must be true.

129>120 is true, but 200<30 is false, so the result of the And is FALSE.

Now that we know that the condition is false, we know that the ELSE statement will be executed.

 

Therefore this statement under the ELSE will be executed:

  intCount = -1

 

Therefore the final value of intCount is -1