Level 3 Computing Year 1 Lecturer: Phil Smith

Transcription

1 Level 3 Computing Year 1 Lecturer: Phil Smith

2 Previously.. We looked at forms and controls. The event loop cycle. Triggers. Event handlers.

3 Objectives for today.. 1. To gain knowledge and understanding of 1. Programming variables a) Local variables b) Global variables 2. Constants 3. Data types 4. Variable naming

4 What are Variables? Variables are an unknown quantity. They are used considerably in programming. So in this expression: x = 22 / 3 What is x?

5 Programming Variables Like empty containers inside the computer Each container is ready to accept a value

6 Variables Can be used to manipulate data Used for mathematical expressions BTEC Level 3 Year 1 - Unit 14 Event Driven Programming

7 Creating a variable 1. Each variable must be created (declared) 1. Created usually before use, but not always 2. You must specify the type of data it will hold 3. This is known as the data type 4. Selection of a variables data type is critical

8 Different Data Types

9 VB.Net Data Types

10 Visual Basic example Dim num1 As Integer Dim num2 As Integer Dim result As Integer num1 = 3 num2 = 8 result = num1 + num2 Variable declaration We have done this already in previous programs.

11 Defining the data type Its important to define the correct data type Think about what data the variable should use/store Cannot store alternative values in specific data types Integer = hello world Integer = 3.56 Boolean = False OK or Error OK or Error Ok or Error

12 Task 1 Work through the variable types worksheet Select a variable type for each input Justify your choice The worksheet is on the WIKI

13 Variable names Like files, variables need correct names Choose a name that best describes the variables use and contents Example Forename ParisTime... ClothesSizes..

14 Data Types

15 Variable Naming No spaces Variables cannot contain any spaces BTEC Level 3 Year 1 - Unit 14 Event Driven Programming

16 Variable Naming Only alpha or numeric characters allowed.

17 Variable Naming Begin with an alpha character. No numbers at the start

18 Variable Naming Each new word starts with capital letter or separated by an underscore Try to use meaningful names. Be consistent.

19 Task 2 Work through Assigning variable names & data types worksheet. Give a proposed variable name and data type for the specific data. The worksheet is on the WIKI.

20 Programming Task Create a Command Line Interface (CLI) program that Calculates your weekly wage amount given: Hours worked Hourly rate

21 Advanced features Add a tax rate and calculate the net wage Include National insurance (8%) Add a yearly projection of the total wage input. Extension: calculates and display the monthly average.

22 Local and Global variables, constants. We need a program to understand local and global variables as well as constants. Re-create the previous program as a GUI based application. You will need labels, textboxes and a calculate button. You need to display the result in a result label, name this lblresult. Name the program weeklywage. The wiki has a suggested code listing.

23 Local and Global variables, constants. We need to look closely at exactly what this program is doing, and the variables/constant it is using.

24 What have your learned? Variables. Variable data types. Data input methods. Variable naming. Summary

25 Control structures in VB.net Next time.. Basic charts