Cross Ref > Language Basics

VB Classic is not case sensitive. If you type any other case for commands or variables, VB Classicwill change it to the "accepted" or "defined" case. For example, if you type msgbox it is converted to MsgBox.

MsgBox ("hello")

Same as standard C++. Both are case sensitive. In C and C++ commands and variable names are case sensitive.

MessageBox::Show("Hello");

messagebox::SHOW("Hello"); //>>>Does not work!

VB Classic code blocks are surrounded by statement ending keywords that all use End such as End Sub, End If, and WEnd.

Sub x

End Sub

If x Then

End If

While x

WEnd

Same as standard C++. For C++, Java, JavaScript, and PHP, I prefer to put the first { at the end of the first line of the code block as in the example above because I see more C++ formatted that way.

class Cyborg {
public: System::Void IntroduceYourself() {
    MessageBox::Show("Hi");
  }
};

Commenting Code
VB Classic, like all the VB-based languages, uses a single quote (') or the original class-style basic "REM" (most developers just use a quote). VB Classic does NOT have a multiple line comment.

Directives - #

Directives are sometimes called compiler or preprocessor directives. A # is used for directives within VB Classic code. VB Classic offers only an #If..then/#ElseIf/#Else directive.

'Single line comment.
 

REM Old school single line comment.
 
#If MyDirective Then
  '...some code.
#End If

 VB Classic Comments (' or REM)

Commenting Code
Same as standard C++. C++ uses "//" for a single line comment and /* */ for a multiple line comment.

//Single line comment in MS (not ANSI compliant so do NOT use).
  

/* ANSI compliant single line comment. */
  

/*
Multiple line
comment.

*/

/*

* This is another popular

* way to write multi-line

* comments.

*/

Scope can be Public, Global, or Private. The use of the newer Public keyword is preferred to the older Global. Private Const is the same as just specifying Const.

Const kPI = 3.1459

Const kName = "Mike"

//Public variable:

Public Const kFeetToMeter=3.28, kMeterToFeet=.3

 VB Classic Constants (Const kPI = 3.1459)

C++/CLI supports the const and static const keywords of standard C++ as well as the new literal keyword. A literal is equivalent to static const in standard C++ and Microsoft's documentation recommends to replace static const with the new literal keyword because a literal is available in metadata; a static const variable is not available in metadata to other compilers.

You can use static const within the class declaration or locally within a method. However, literal is only valid in the class declaration section and const is only valid within a method.

Syntax Example:   //some method { const String^ MyName = "John"; static const Int32 MyAge = 27; //} // public class SomeClass : public Object { public:   literal double Pi = 3.14159;   literal String^ MyName = "Mike";   static const Int32 MyAge = 35; //...

 Ref: http://msdn.microsoft.com/en-us/library/ms235301(VS.80).aspx

A return marks the end of a statement and you cannot combine statements on a single line of code. You can break a single statement into two or more code lines by using a space and underscore " _".

MsgBox "Hello1"
MsgBox "Hello2"
MsgBox "Hello3"
 
'The following commented code 
'on a single line does not work...
'MsgBox "Hello4"  MsgBox "Hello5"
 
'Two or more lines works too with a space+underscore:
MsgBox _
 "Hello6";

Same as standard C++. C++ uses a semicolon ";" as an end of statement specifier and you can put multiple statements on a single line of code if you wish as well as split a single statement into two or more code lines.

//.Net WinForms example.

//Add, using namespace System::Windows::Forms;

MessageBox::Show("Hello1");

MessageBox::Show("Hello2");

MessageBox::Show("Hello3");

MessageBox::Show("Hello4"); MessageBox::Show("Hello5"); 

MessageBox:: 

  Show 

    ("Hello6");

String literals are quoted as in "Prestwood". If you need to embed a quote use two quotes in a row.

To specify a floating point literal between 1 and -1, you can preceed the decimal with a 0 or not (both work). In other words, preceding and following decimals are allowed (both .1 and 0.1). Trailing decimals are optimized out and replaced with # if only integer values are used.

MsgBox ("Hello")

MsgBox ("Hello ""Mike"".")

'Does VB evaluate this simple

'floating point math correctly? No! 

If (.1 + .1 + .1) = 0.3 Then
  MsgBox "Correct"
Else
  MsgBox "Not correct"
End If

Same as standard C++. String literals are quoted as in "Prestwood". If you need to embed a quote use a slash in front of the quote as in \".

To specify a floating point literal between 1 and -1, you can preceed the decimal with a 0 or not (both work). In other words, preceding and following decimals are allowed (both .1 and 0.1). Trailing decimals are also allowed (1, 1., and 1.0 are all equivalent and allowed).

MessageBox::Show("Hello");

MessageBox::Show("Hello \"Mike\".");

//Does ASP evaluate this simple

//floating point math correctly? No! 

if ((.1 + .1 + .1) == 0.3) {
  MessageBox::Show("Correct");
} else {
  MessageBox::Show("Not correct");
}

VB Classic is a loosely typed language. Declaring variables is optional unless you use the Option Explicit statement to force explicit declaration of all variables with Dim, Private, Public, or ReDim. Using Option Explicit is strongly recommended to avoid incorrectly typing an existing variable and to avoid any confusion about variable scope.

Undeclared variables are variants. To specifically declare a variant, use:

Dim x As Variant

Dim x 

Common data types include Byte (0..255), Boolean, Integer (2-byte integers), Long (4-byte integers), Currency, Single (32-bit number), Double (64-bit number), Date, String, and variant.

Variables declared with Dim at the module level are available to all procedures within the module. At the procedure level, variables are available only within the procedure.

Dim FullName As String
Dim Age As Integer
Dim Weight As Double

FullName = "Mike Prestwood"

Age = 32

Weight = 154.4

'Declaritive assignment not supported:

''Dim Married As String = "Y"   '>>>Not supported.

 VB Classic Variables (Dim x As Integer)