Variables in VB

What is a variable?►A named memory location that stores

a value

Why use variables?►Makes code easier to read►Used to transfer information from one

part of a program to another

Types of VariablesTYPE PREFIXSingle sglDouble dblInteger intLong lngCurrency curString strBoolean bln

Single►Positive or negative real (might

contain a decimal) numbers►Can store smaller numbers

Double►Same as single, but can store larger

numbers

Integer►Positive or negative integers (no

decimals)►Smaller integers►Good for counting (e.g. number of

students in a class)►NOTE: if a decimal number is assigned

to an integer, then the value is rounded

►E.g. 6.7 would become 7

Long►Same as integer, but can store larger

numbers

Currency►Real numbers that are money values►Up to four decimal places

String►Set of characters (e.g. letters or any

character that can be typed)►String assignments require quotation

marks “” ►E.g. strword = “hello”

Boolean►True or false►Used for on/off and yes/no values

Using VariablesStep 1 – DeclareStep 2 – Initialize (Assign a value) Step 3 – Use

Declaring VariablesE.g.

Dim intage As Integer

►Dim - stands for dimension (a variable has been assigned a space in memory somewhere)

►intage – identifier (name of variable)►Integer – data type

Declaring VariablesWhen a variable has been declared, you have

saved a space in memory to hold whatever value is assigned:

intage

Initializing Variables (assigning a value)

E.g.intage = 15 OR

intage = txtage.text

This will assign whatever the user types into the textbox to intage.

Initializing Variables► The space in memory now holds a value

15

intage

Using the VariableE.g.intagedoubled = intage * 2

This will calculate the person’s age multiplied by 2 and then will store it in the variable called: intagedoubled.

You can then output the variable intagedoubled to a textbox.

txtagedoubled.text = intagedoubled

Questions1 – Write a variable declaration

statement for:a) A variable called intgrade of integer

type

b) A variable called strword of string type

Questions2 – Indicate the value of the following

variables:a) Dim dblnumber As Double

dblnumber = 6 – 3

dblnumber

Questions2 – b) Dim intnum1 As Integer

Dim intnum2 As Integer Dim intnum3 As Integer

intnum1 = 3intnum2 = 4intnum3 = intnum1 * intnum2

intnum1 intnum2 intnum3