Tutorial 3

 

Variables

            Types

                        Byte - 0 to 255   (byt)

                        Boolean            - TRUE or FALSE          (b)

                        Currency - Number up tp 15 digits to left of decimal and 4 digits to right      (cur)

                        Date - 1/1/100 - 12/31/9999            (dtm)

                        Double - +-5E-324 to 1.8E308            (dbl)

                        Integer - 32768 to 32767              (int)

                        Long - +- 2 billion                     (lng)

                        Single - +- 1E-45 to 3E38     (sng)

                        String - text 1 to 65,400 characters (str)

                        Variant - any other type             (var)

            Naming

                        begin with letter

                        letters, digits, underscore

                        not more than 255 characters

                        cannot be a reserved word

            Declaring

                        Dim            Dim {variable name} as {datatype}

                        Public            Public {variable name} as {datatype} - Global Variables

            Constants

                        Literal Constant - an item of data whose value does not change ex. 500

                        Symbolic Constant - memory location whose contents do not change

                                                            while program is running

                                    Const {constant name} as {datatype}

                                                Const strPath = "C:\temp"

                                                Const pi as double = 3.14

                                    Public Const {constant name} as {datatype}

 

            Scope

                        objects event procedure

                        form

                        code module declaration seciton - global variables

 

            Option Explicit

                        requires declaration of all variables, without it any variable that is not declared witn                  DIM or Public is type integer

 

Code Module

            separate file that contains code

                        Choose Project on menu bar, Add Module(bas extension)

           

Concatenating Strings

            strTemp = "Help" & " " & "me"

            strTemp2 = strTemp & " the end."          

 

InputBox Function

            InputBox(prompt,title)

            strName = InputBox("Name","Enter Name Dialog")

vbNewLine character

            symbolic constant

            chr(13) & char(10)

Default Button

            Button chosen whenver {enter} is presses

            set default property of button

 

Adding a form

            Existing form

                        choose project menu, Add Form

Specifying Startup form

            Project properties

Form Statements

            Load - brings form into memory - Load {formname}

            Unload - removes form from memory - UnLoad {formname}

Form Methods

            {form}.Hide - Hides the form

            {form}.Show - Display form

Types of forms

            modeless - can take action on other forms in applications

            modal - no action can be taken on another form in application until form is unloaded or hidden

 

Center form on scree

            {formname}.Top =(screen.Height - {formname}.Height/2

            {formname}.Left =(screen.Left - {formname}.Left/2

 

Timer Control

            to perform some action at specified time intervals

            Interval Property - set im millisecomds

            Place code in Timer event