1. CS 106 Computing Fundamentals II Chapter 71 “Indexing”
Herbert G. Mayer, PSU CS
Status 7/24/2013
Initial content copied verbatim from
CS 106 material developed by
CS professors: Cynthia Brown & Robert Martin

2. Syllabus Indexing String Structure Indexing Listboxes
Some Useful Properties

3. Indexing
Indexing is the process of selecting one of multiple elements from an aggregate datum:
A typical aggregate data structure is the array or string
The selection is called “indexing”
In simpler languages, the index is an integer numeric value
More sophisticated languages allow other index types
The index range is contiguous, starting at 0 or 1
It’s like having an address where you need a house number as well as a street name
Indexing often “cycles” through all contiguous items in a linear fashion, using a loop

4. String Structure
A string in VBA can be variable length and has an internal structure
Each character in the string also has a position number, also called an index
The first character in a string however has index 1, etc
String “This is a string.” has 17 characters, counting the blanks and period ‘.‘: T h i s a t r n g . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

5. Indexing in Listboxes
We used listboxes as a place to print information on a user form
But they can also be used as a flexible way to store and access information
The workbook called IndexListBox has examples of how to use these features
One important fact: indexing in a listbox starts at 0 instead of 1

6. Some Useful Properties
lstName.Listcount is the number of items in list box lstName
lstName( anIndex ) is the item in the listbox lstName with index anIndex
lstName.ListIndex is the index of the selected item in the listbox

7. Demo: Index ListBox