1. Chapter 6 Looping Structures

2. Do…LoopDo…Loop Statement Can operate statements repetitively Do intx=intx + 1 Loop While intx < 10 –The Loop While operates the statement at least once Do While intx < 10 intx=intx + 1 Loop

3. Infinite Loops May have problems with loops –Logic error –Overflow error –Infinite Loop

4. Input Box Pop-up text box that allows the user to input information Has a prompt, text box, OK and cancel button How to display: strx = InputBox(“prompt”, “title”) intx = val(strx) me.lbl.text = intx If text box is blank = nothing

5. Accumulator Variables Variable that stores an accumulating score Keeps a running total or sum Just like a counter intTotal = intTotal + intScore Keep in mind if you’re adding decimals or integers

6. Flags or Sentinels Something significant in your program that stops program execution or ends a loop Generally declared as a constant Inputbox(“Enter a positive number (-1 to finish)”)

7. For…Next Statement Looping structure that performs a set number of times Operates until a counter reaches an ending value

8. String Class The string data type is a class containing multiple properties String class properties:

9. String Class Example: Think of a String as a row of numbered boxes. The first boxe’s number is zero and they go up from left to right. Only one letter can be in each box. 0 1 23 4 5 SUMMER

10. String Methods Methods are procedures within a class.ToUpper.ToLower.Trim.TrimEnd.TrimStart.PadLeft(length,”char”).PadRight(length, “char”)

11. String Substring These return a portion of the string.Substring(startPos, numOfChars).Remove(startPos, numOfChars).Replace(oldString, newString).Insert(startPos, substring).IndexOf(substring)

12. String Class Examples Dim strSeason As String = “SummerTime” Dim strNewString As String strNewString = strSeason.ToUpper ‘SUMMERTIME strNewString = strSeason.ToLower ‘summertime strSeason = “ SummerTime “ strNewString = strSeason.Trim ‘SummerTime strNewString = strSeason.TrimEnd ‘ SummerTime strNewString = strSeason.TrimStart ‘SummerTime

13. Examples Cont… strSeason = “SummerTime” strNewString = strSeason.PadLeft(15, ”x”) ‘xxxxxSummerTime strNewString = strSeason.PadLeft(9, “x”) ‘SummerTime strNewString = strSeason.PadRight(13, “x”) ‘SummerTimexxx

14. Examples Cont… Dim strSeason As String = “SummerTime” Dim strNewString As String Dim intPos As Integer strNewString = strSeason.Substring(6,4) ‘Time strNewString = strSeason.Remove(0,6) ‘Time strNewString = strSeason.Replace(“Time”, “ is fun!”) ‘Summer is Fun strNewString = strSeason.Insert(6, “ is a fun “) ‘Summer is a fun Time intPos = strSeason.IndexOf(“mer”)‘3

15. String Concatenation Join two or more strings together String.concat(string1, string2) The & operator also joins strings To add spaces use empty quotes or Space(#) The Space function will add a stated number of spaces vbTab adds 8 spaces, vbCrLf - returns

16. Char Structure A structure is a simple form of a class Like the class, a structure has properties chr1 = char.ToUpper(chr2) chr3 = char.ToLower(chr2)

17. Comparing Strings Used to alphabetize a list Compare(string1,string2,Case-insensitive) –Case-insensitive should be true or false True-case is not considered, a, A 0-string1 and string 2 equal 1-string1 is after string2 -1-string1 is before string2

18. Like Operator The Like is used as a Boolean expression –String1 Like String2 –True if String1 matches the pattern of String2 –False if there is no match –? Used for a single character –* used for many characters –# used for a single number –[] used to enclose a list of characters – used to indicate a range of characters in a character list –, used to separate characters in a character list