Data structures vb
- 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