1. Data structures
in VB.NET
1

2. Processing
Once the data has been entered into the
program, we need to “do something with it”
This is the data processing part
Most of what you want to do to it has been
done before – many times!
There are some standard “structures” that it
is useful to know about
2

3. How a program runs
Variables have a space reserved in
memory (they are declared and initialised)
They might be given a value
The next lines in the program or part of
the program that is running are read and
executed one at a time
3

4. Conditional statements
We might want a program to make some
choices based on the data it receives
e.g. If intAge > 17 then…..
The full syntax in VB is:
If condition Then
Line of code to execute
End If
4

5. Conditional statements
Don‟t forget the End If!
It is also possible to add another condition,
a kind of „either or‟ choice:
If condition Then
Line of code to execute
Else
Another line of code if the above
condition is false
End If
5

6. Conditional statements
Whole banks of If…Then statements can be
built up to test for various conditions
If there are many, this can get confusing and
messy
Far better in this case to use the Select Case
statement
6

7. Conditional statements
Syntax:
Select Case variable
Case possible value or range
Line of code to execute
Case another possible value
Another line of code
End Select
7

8. Loop structures
These are used when we want lines of code to
be executed many times
How many times depends on either various
conditions being met or we might want it to
run a set number of times
There are loops for all occasions and
programmers have their favourites!
8

9. Loop structures
If we want the loop to run a fixed number of
times, we use a For…..Next loop
This will use a variable as a counter
Syntax:
For first value To last value
Line of code to execute
Next value
9

10. For...Next example
10

11. Loop structures
If you want the loop to carry on an unspecified
number of times until a condition is met,
use a Do….While Loop
Beware! It is possible to create loops that carry on to
infinity
Infinite loops aren‟t the end of world – the computer
may crash so you might lose some unsaved work
Pressing Ctrl + Break sometimes works to stop it
11

12. Loop structures
Syntax:
Do While value=whatever
Line of code to execute
Loop
Or (my favourite):
While value=whatever
Line of code execute
End While
12

13. While…End While Example
13

14. Loop structures
Loops can also be nested
This is where it can get really confusing
One loop can search through one set of data
But it can be running inside another loop
This is useful where data is in a table
One loop deals with rows
The other deals with columns
14

15. Loop structures
When nesting loops, it is important to get the
code looking tidy
The best way to do this is with indentation
The section of code after the first line is tabbed in
The last line is tabbed out
15

16. Code Example
This is a neat piece of code
(of course, I wrote it )
It contains two loops – an inner and an outer
Can you try to work out what it does?
16

17. Programming terms
In this session we have covered the three
ways that programs flow
Sequence – running one line after another
Selection – using conditional statements
Iteration – using loops
17