Talk:Visual Basic/Introduction

I just made a whole lot of new content for this page. Good luck sifting through it! :-D

Some places to link to or somehow incorporate knowledge from:

• http://hashvb.earlsoft.co.uk/Main_Page
• Anything on this list: http://en.wikiversity.org/wiki/Special:Search?search=vb6&go=Go
  • http://en.wikiversity.org/wiki/API_use_with_VB6
  • http://en.wikiversity.org/wiki/Variables_and_Types_in_VB6
  • http://en.wikiversity.org/wiki/Functions_and_Subroutines_in_VB6

A place to chat with the people involved in this project would be nice so we're not stepping on eachothers' toes. I'm new to wikiversity, et al. I just figured out the basic structure of the courses, so I'm trying to work with that. I think some more brainstorming about course plan structure would be a good idea.

Removed content...

I just removed the following content from this page. It's useful information, but highly inappropriate to an introductory article. Let's see if we can't find a better place for it. AmiDaniel (talk) 18:51, 1 March 2007 (UTC)

Object Types and Naming Scheme

These are very important things to remember in order to make your source code more easily intelligible.

File Types

You will use various file types while using VB6. These are some the most common ones.

• File type: What people call it
• Prefix: What people prefix the filename with
• Extension: What file extension is used
• Description: What its used for most often

File Type	Prefix	Extension	Description
Project		vbp	General project options
Form	frm	frm	GUI information and private code
BAS Module	mod	bas	Project-wide accessible functions
Class Module	cls	cls	Project-wide accessible subroutines
User Control	uc	ctl	Control object (Like an OCX with source code)
Property page	pag	pag	Property information
OLE Control		ocx	Compiled control object
Dynamic Link Lib		dll	Subs and functions accessible by other programs

Examples of common file names:

• OddCalc.vbp
• frmMain.frm
• frmAbout.frm
• frmPrintInvoice.frm
• modMain.bas
• modSettings.bas
• modDeclares.bas
• modWinsock.bas
• clsWinsock.cls
• ucCustomButton.ctl
• ucTreeView.ctl
• ucWinsock.ctl

Variables

A variable is a word or letter used to reference data used in a program. At the most basic level: All variables used in a program (Even if its interpreted as text) are held on the computer as a sequence of 1s and 0s (Binary) which represent numbers, which may or may not in turn represent letters or any given ASCII character.

In a sane programmer's code the variable names are easy to understand because they clearly state what the variable is used for inside of the variable name.

The information to be conveyed in a variable name is:

1. Variable data type
2. Functional use in program

This is accomplished by coming up with a unique word between about 3 and 10 letters which explains the functional use of the variable as well as a prefix of usually 3 letters which explains the variable data type.

A few examples of this:

• intResult -- An integer which is the result of an operation
• strFirstName -- A string which is used to store the first name of a person
• dtmWorkDayEnd -- A Date variable which is used to store the time of the end of the work day

Computer Data Storage

All data stored on a computer is based upon binary values associated with them somewhere between 0 and 255. This is the range of values possible with an 8 bit binary value (8 ones and zeroes).

Decimal	Binary	Hexadecimal	ASCII
48	0b00110000	0x30	0
49	0b00110001	0x31	1
50	0b00110010	0x32	2
-------	---------------	---------	-----
55	0b00110111	0x37	7
56	0b00111000	0x38	8
57	0b00111001	0x39	9
-------	---------------	---------	-----
65	0b01000001	0x41	A
66	0b01000010	0x42	B
67	0b01000011	0x43	C
-------	---------------	---------	-----
88	0b01011000	0x58	X
89	0b01011001	0x59	Y
90	0b01011010	0x5A	Z
-------	---------------	---------	-----
97	0b01100001	0x61	a
98	0b01100010	0x62	b
99	0b01100011	0x63	c
-------	---------------	---------	-----
120	0b01111000	0x78	x
121	0b01111001	0x79	y
122	0b01111010	0x7A	z

A text character's "ASCII value" is the decimal value of the binary value used to represent that character on the computer. In the case of the uppercase letters A, the ASCII value is 65, which is 01000001 in binary. Uppercase Z has an ASCII value of 90, which is 1011010 in binary. The values for uppercase letters A through Z are between the values 65 and 90.

Anybody notice how similar the uppercase and lower case values are in binary and hex? In binary you toggle the 32's place in order to change case, and in hex you add/subtract 2 from the 16's place. Handy.

Associated example to play with:

Option Explicit

Private Sub Form_Load()
Dim strChar As String ' Declares a variable
    
    ' Shows an input box and puts the result in a variable called strChar
    strChar = InputBox("What would you like the ASCII value of?", "HUH!? PUNK!?", "A")
    
    ' Shows a message box containing the ASCII value of the previously input letter
    '   plus a random ASCII uppercase letter
    MsgBox "The ASCII value of " & strChar & " is " & Asc(strChar) & vbNewLine & _
            "And your random, uppercase ASCII character is: " & _
                Chr$(RandomNumInRange(65, 90))
    
    ' Unloads the form (Which cleanly ends the program if no other forms are loaded)
    Unload Me
End Sub

Public Function RandomNumInRange(ByVal Low As Long, ByVal High As Long) As Long
    Randomize ' Randomizes Rnd() (Surprisingly good random number generator)
    
    ' Generates a random number between "High" and "Low" and returns it
    RandomNumInRange = Int((High - Low + 1) * Rnd) + Low
End Function

Variable Names

The following are the requirements when naming the variables in Visual Basic:

• It must be less than 255 characters
• No spacing is allowed
• It must not begin with a number
• Period is not permitted

For the sake of making sure other people can look at your code and know what the hell you were thinking:

• Suffix your variable name with the appropriate suffix for your variable's data type
• Make sure the body of your variable name makes it easy to tell what its used for
• Don't use an ambiguous name like "intUhhhh" or "strX" unless its use is within a very small scope of the program

Numeric Data Types

Type	Size	Range of Values	Prefix	Example Variable Name
Byte	1 byte	0 to 255	byt	bytFirstChar
Integer	2 bytes	-32,768 to 32,767	int	intCount
Long	4 bytes	-2,147,483,648 to 2,147,483,648	lng	lngHwnd
Single	4 bytes	Negative values: -3.402823E+38 to -1.401298E-45 Positive values: 1.401298E-45 to 3.402823E+38	sng	sngPi
Double	8 bytes	Negative values: -1.79769313486232e+308 to -4.94065645841247E-324 Positive values: 4.94065645841247E-324 to 1.79769313486232e+308	dbl	dblAngle
Currency	8 bytes	-922,337,203,685,477.5808 to 922,337,203,685,477.5807	cur	curTotalCost

Non-numeric Data Types

Type	Size	Range of Values	Prefix	Example Variable Name
String(fixed length)	Length of string	1 to 65,400 characters	str	strName
String(variable length)	Length + 10 bytes	0 to 2 billion characters	str	strHTML
Date	8 bytes	January 1, 100 to December 31, 9999	dtm	dtmBirth
Boolean	2 bytes	True or False	bln	blnToggle
Object	4 bytes	Any embedded object	obj	objCurrent
Variant(numeric)	16 bytes	Any value as large as Double	vnt	vntNumber
Variant(text)	Length+22 bytes	Same as variable-length string	vnt	vntName

Control Types

Control Type	Prefix
TextBox	txt
PictureBox	pic
Label	lbl
Frame	fra
CommandButton	cmd
CheckBox	chk
RadioButton	rad
ComboBox	cbo
ListBox	lst
Scroll Bar	sbr (no orientation needed)
Timer	tmr
DriveListBox	drv
DirListBox	dir
FileListBox	fil
Shape	shp
Image	img
Data	dat
OLE	ole
ListView	lvw
TreeView	tvw

Examples of common object names:

• txtName
• txtAddress
• cboYear
• cmdOK
• cmdCancel

General Overview of Coding

Routine Types

• Sub: Returns nothing
  • Example:

' Description: Makes the window caption a random number between 1 and 100 every time the form is clicked

Option Explicit

Public intRandom As Integer

Private Sub Form_Click()
    Call GetNewRandom
    Me.Caption = intRandom
End Sub

Public Sub GetNewRandom()
    Randomize
    intRandom = Int(Rnd() * 100) + 1
End Sub

• Function: Returns some sort of value
  • Example:

' Description: Makes a message box which displays the current military time at form load.
Option Explicit

Private Sub Form_Load()
    MsgBox "Current military time is: " & GetMilitaryTime
End Sub

Public Function GetMilitaryTime() As String
    GetMilitaryTime = Format$(Time, "hh:mm:ss")
End Function

Specific to user controls:

• Let
• Get
• Set