This document provides an overview of one-dimensional arrays in Visual Basic. It discusses that arrays allow storing multiple values in one variable, with each element distinguished by its subscript index. The Dim statement is used to declare an array, specifying the array name and size. Arrays store similar element types, and elements can be accessed and assigned values using their index. Dynamic arrays can change in size at runtime using the ReDim statement. Methods for populating, searching, and modifying array elements are demonstrated. Common array errors like failing to use the Preserve keyword when resizing are also addressed.

1. MODULE 12
ONE DIMENSIONAL ARRAYS

2. Welcome to Module 12!
• In this unit, we will introduce the concept of arrays.
Throughout this course, it was understood that variables can
store one (and only one) value.
• In this unit, we discuss that there is one structure that CAN
hold more than one value: an array.
• Arrays are great tools for storing a group of similar (or
dissimilar, in some cases) items of data.
• We will discuss how arrays are created, how items are stored
in arrays, and how you can search and retrieve items from
them.

3. WHAT IS AN
ARRAY?
• Allows
programmers to
represent many
values with one
variable name
• Elements in the
array are
distinguished by
their subscript

4. THE DIM
STATEMENT
FOR ARRAYS

5. Eggs as elements
in an Array
• Arrays are items that can store
a collection of related, or
similar, values that can be
referenced individually by their
indices. One way to picture an
array is to think of a container
of similar objects that only has
a certain number of slots. The
egg carton itself is the
container, and each egg is a
variable. You can reference
each egg by its index: egg 1,
egg 2, and so on. This allows
you to store similar elements
together.
Image source: http://flylib.com/books/en/4.226.1.41/1/

6. Eggs as elements
in an Array
• Arrays in Visual Basic are
zero-based, meaning that the
first item in an array is stored
at index 0. Thus, the last
item's index array is always
one minus the number of
items in the array. All
variables in an array must be
of the same data type—you
can't mix and match
• So we need to change our
image a little
Image source: http://flylib.com/books/en/4.226.1.41/1/

7. Eggs as elements
in an Array
• When you set up an array with
the Dim word, you put the name
of your array variable, and tell
Visual Basic how many items
you want to store in the array.
• But you need to use
parentheses around your
number. You then assign your
data to a position in the array. In
our Egg example:
• Dim myEggCarton(11) As Integer
Image source: http://flylib.com/books/en/4.226.1.41/1/

8. ARRAYS
• Take a look at the picture below:
• In order to create an array, we use the following
syntax:
• Dim strNames(4) As String

9. ARRAYS
• We could then populate our array with names as
follows:
• Dim strNames(5) As String
• We could then populate our array with names as
follows:

10. ARRAYS
• An easier way would be to use For…Next loops to
populate the array.
• You set up the loop with a counter.
• The loop goes from 0 to 5 (6 total iterations) and each
time an input box is generated, allowing the user to
input a name.
• This can be accomplished in the following manner:

11. SEARCH ARRAYS
• Always use a For…Next Loop
• Example:
For intCounter = 0 to intNumbers.Length-1
If intNumber(intCounter)= 5 Then
MessageBox.Show(“The number has been found”)
Next
• What does this do – first it looks at intNumber(0) and sees if it is 5, then it
looks at intNumber(1), etc .
• Whenever it “sees” a 5 it pops a MessageBox

12. DYNAMIC ARRAYS
• Dynamic Array- Can differ in size at run time
• Dim intNum(-1) - (-1) means that the array is dynamic.
• ReDim –Used to change the size of an array
• Preserve – preserves elements so they are not cleared.

13. EXAMPLE
• Dim intTestScores(-1) As Integer
• Dim intNumberOfScores As Integer
• intNumberOfScores=inputbox(“How many test scores would
you like to enter?”)
• Redim intTestScores(intNumberOfScores) As Integer
For intCounter 0 to intTestScores.Length-1
IntTestScores (intCounter)=InputBox(“Enter Score Here”)
Next
-1 indicates a dynamic array
Redim changes the size of the array

14. ERROR ALERT
WHY IS MY DYNAMIC
ARRAY ALL ZEROS?

15. A Couple of Errors in the Course
• In slide 5 of the tutorial you add this code:
• In slide 6 of the tutorial you are SUPPOSED to modify ( or
replace) that code with this code:
• If you didn’t preserve, then you are displaying the cleared
array – and you will get those zeros.

16. A Couple of Errors in the Course
• Dynamic Tutorial - The video is fine with this one, but in
the steps - it tells you to double click on btnSearch and it
should be btnDynamic
• Slide 7 on Tutorial 4 has the wrong image – should be:
• The above image is in the instructions so you can
reference it