CSE 100: Lab, May 6

Array Variables and Indexing

keep this picture in mind

some key points

• kind of like a numbered collection of variables, all of the same type

• has one name, so indexing lets you get to the elements of the array:

     authorArray(index)

  Note that index must be an Integer.

  You can index with any expression that ends up being an Integer, so this is okay, as long as i was declared an Integer variable earlier:

     authorArray(i) = "Twain"

  This comes in handy later with loops...

• declaration syntax:

     Dim array_name(max_index) As type

  Note that the Integer in parenthesis is the maximum index for the array, which is one more than the number of elements, because Visual Basic numbers elements starting from 0, not 1.

• You can use an array element anywhere Visual Basic expects a value whose type is the same as the array type.

  With the example array authorArray above, it's alright for me to do this:

     MsgBox "Why not read something by " & authorArray(5) & "?"

  or this, an assignment:

     authorArray(3) = "Angelou"

• Arrays variables, just like regular variables, have scope. If you declare an array inside a Sub, it is a local array, i.e. it only exists while the Sub is running and is not visible outside the Sub.

  If you declare an array at the top of your code, right after Option Explicit, it is a global array, i.e. it exists during the whole time your program is running and is available toi all Subs.

array vocabulary

• element - one member of the collection of storage locations of an array
• index or subscript - the Integer value used to identify a specific element of an array

What's up with these?

If authorArray(7) = "Naipaul" Then ...

authorArray("two") = "Melville"

MsgBox "Read any " & authorArray & " lately?"

Case Select authorArray(1.5) ...

looping through arrays

Sub pesterMeAboutReading()
  Dim i As Integer

  For i = 0 to 5
    MsgBox "Go read some " & authorArray(i) & "!"
  Next i
End Sub