Controlling Program Flow 091700

Topics Conditional Operators Logical Operators If Select Case Loops

Operators manipulate data by combining or computing results.

Math and String Operators Already Covered ( ) ^ * / \ MOD + - &

6 Conditional Operators = Equal to < Less than > Greater than <> Not equal (less than or greater than) <= Less than or equal to >= Greater than or equal to NOTE: Errors is textbook table 6.1

You can compare strings “S” < “s” “Kev” < “Kevin” ASCII table for character values Appendix C, page 888 IMPORTANT: The computer ultimately gives comparisons a TRUE or FALSE answer. print (1<2) print (1=2)

Like Operator Used for seeing if strings are similar Uses Wildcards: * ? # [characters] [!not these characters] print “Kevin” like “Ke*” print “Boot” “B??t” print “Beet” like “B??t” print “Employee 7” like “Employee #” NOTE: Wildcard comparison has to be AFTER the like operator. Book is misleading here.

Logical Operators And Or Xor Not

And …Statements If (varA = varB) And (varC < varD) then End if If True and True then Condition 1 AND Condition 2

Or …Statements If (varA = varB) Or (varC < varD) then End if If True Or True then Condition 1 AND Condition 2

Xor …Statements If (varA = varB) Xor (varC < varD) then End if If True Xor True then Condition 1 AND Condition 2

Not …Statements If Not((varA = varB) And (varC < varD)) then End if NEGATES a condition Use Sparingly!

Truth Table Condition Result AND TRUE FALSE OR XOR

Such a simple device… Computers only know: 1 or 0 ON or OFF Yes or No True or False We combine these choices to set the course of our computer program.

If then If (condition is true) then do this End if

If then Else If (condition is true) then do this Else do something else End If

If then ElseIf If (condition is true) then do this ElseIf (condition is true) then do something else Else do yet something else End If

Select Case Simpler, more logical than using several elses Select Case varAge Case Is <5 statements Case 5 Case 6 to 11 Case 12 to 13, 23 to 46, Is 65 Case Else End Select

For Next Loop Used for counting through a certain number of iterations (geek-speak for times). For Counter = 1 to 10 statements Next

Nesting Loops For outerCounter = 1 to 10 statements For innerCounter = 1 to 10 Next innerCounter Next outerCounter

Step value For counter = 0 to 10 step 2 statements Next

Step Values: negative For counter = 10 to 0 Step -1 statements Next

Do Loops Execute WHILE a condition is true, or UNTIL it is true Do While strAnswer=“yes” statements Loop

Do Loops Do While Loop condition Until

Do Loops Do While condition statements Loop Do statements Loop While condition Do Until condition statements Loop Do statements Loop Until condition

An early exit… Exit Sub Exit Function Exit For Exit Do Use sparingly - It is most clear to have one exit for a program segment