‘Visual Basic’

Developer: Microsoft
Appeared in: 1991; 24 years ago
OS: Microsoft Windows and Ms - DOS

HISTORY: Alan Cooper, the 'father' of Visual Basic, shows a drag-and-drop shell prototype called Tripod to Bill Gates. Microsoft negotiates to buy the concept, now code-named Ruby. The Tool includes a widget control box, the ability to add widgets dynamically, and a small language engine.

Visual Basic is Microsoft's high-level object-oriented rapid application development environment for the Windows platform. The first versions of Visual Basic were intended to target Windows 3.0 (a version for DOS existed as well), however it was not until version 3.0 for Windows 3.1 that this programming language gained large-scale acceptance in the shareware and corporate programming community. VB 1.0 was introduced in 1991. The approach for connecting the programming language to the graphical user interface is derived from a system called Tripod (sometimes also known as Ruby), originally developed by Alan Cooper, which was further developed by Cooper and his associates under contract to Microsoft.

Visual Basic is a third-generation event-driven programming language and integrated development environment (IDE) from Microsoft for its COM programming model first released in 1991. Microsoft intended Visual Basic to be relatively easy to learn and use. Visual Basic was derived from BASIC and enables the rapid application development (RAD) of graphical user interface (GUI) applications, access to databases using Data Access Objects, Remote Data Objects, or ActiveX Data Objects, and creation of ActiveX controls and objects. * A data access object (DAO) is an object that provides an abstract interface to some type of database or other persistence mechanism. By mapping application calls to the persistence layer, DAO provide some specific data operations without exposing details of the database. * Remote Data Objects (abbreviated RDO) is the name of an obsolete data access application programming interface primarily used in Microsoft Visual Basic applications on Windows 95and later operating systems. * ActiveX Data Objects (ADO) is an application program interface from Microsoft that lets a programmer writing Windows applications get access to a relational or non-relational database from both Microsoft and other database providers.

The Evolution of Visual Basic. Visual Basic 1.0 for Windows was first released on May 20, 1991 at the Windows World convention in Atlanta Georgia. In September 1992, Microsoft announced Microsoft Visual Basic for MS-DOS in Standard and Professional editions. Like Visual Basic for Windows, this version combined the ease of graphical design with the power and versatility of traditional programming. Developers simply drew the user interface and attached code that responded to events. However, following the release of Windows 3.1 in March 1992 it became apparent that the DOS environment had come to the end of its useful life. The last version of MS-DOS, 6.22, was released in 1994. VB version 2.0 for Windows (November 1992) was faster, more powerful and easier to use than version 1. VB 2 was also available in a freeware student release called the Primer edition. Visual Basic 3.0 (1993) added tools to access and control databases and Object Linking and Embedding (OLE) version 2. It came in Standard and Professional versions. A superset of VB, called Visual Basic for Applications, was released as part of Microsoft Excel 5 and Microsoft Project 4 in 1993. It has since become the internal programming language of the Microsoft Office family of products, and is available for license by other software companies. Visual Basic 4 was released in 1995 and supported the new Windows 95 family of 32-bit operating systems. The Professional Edition could also compile code to run on the older 16-bit Windows 3.x systems. Visual Basic Scripting Edition (VBScript) was also announced in 1995. VBScript is used to write embedded code for inclusion in web pages, although not all web browsers will run VBScript. With the introduction of Visual Basic version 5 in early 1997, 16-bit systems were no longer supported. Between versions 4 and 5, significant changes were made in the user interface. Visual Basic 5 added, among other things, the ability to create true executables and to create your own custom controls. It also supported Microsoft's Active-X technology. Visual Basic 5 was available in Standard (Learning), Professional and Enterprise Editions. A free edition, called Control Creation Edition, could be downloaded from www.microsoft.com, and was included with many textbooks. Visual Basic 5 was also included as part of a package known as Visual Studio 97. Visual Basic 6 (VB6) was introduced in 1998 and was included as part of a package known as Visual Studio 6.0. VB6 added new capabilities in the areas of data access, Internet features, controls, component creation, language features and wizards. The newest version of Visual Basic, sometimes referred to as VB7 or Visual Basic .NET, was released in February 2002. This product will be part of Microsoft's .NET software initiative, designed to produce XML-based applications for the Microsoft Internet environment. A Microsoft Web article says, «At first glance, it may appear to you that Visual Basic .NET is so radically different from what you know that you will have to learn it all over again.» For more information on Visual Basic .NET, see the article upgrading from Visual Basic 6.0 on the Microsoft Web site.

The three steps in creating a Visual Basic program: 1. Create the interface; that is, generate, position, and size the objects. 2. Set properties; that is, configure the appearance of the objects. 3. Write the code that executes when events occur

Relational Operator -is a programming language construct or operator that tests or defines some kind of relation between two entities. These include numerical equality (e.g., 5 = 5) and inequalities (e.g., 4 ≥ 3).

greater than | > | greater than or equal to | >= | less than | < | less than or equal to | <= | equal to | = | not equal to | <> |

Logical Operators
The logical operators are described in the following table: Operator | Usage | Description | Logical AND (&&) | expr1 && expr2 | Returns expr1 if it can be converted to false; otherwise, returnsexpr2. Thus, when used with Boolean values, && returns true if both operands are true; otherwise, returns false. | Logical OR (||) | expr1 || expr2 | Returns expr1 if it can be converted to true; otherwise, returnsexpr2. Thus, when used with Boolean values, || returns true if either operand is true; if both are false, returns false. | Logical NOT (!) | !expr | Returns false if its single operand can be converted to true; otherwise, returns true. |

Logical AND (&&)
The following code shows examples of the && (logical AND) operator.

A1 = true && true // t && t returns true
A2 = true && false // t && f returns false

Logical OR (||)
The following code shows examples of the || (logical OR) operator.

A1 = true ll true // t ll t returns true
A2 = false ll true // f ll t returns true

Logical NOT (!)
The following code shows examples of the !(logical NOT) operator.

A1 = !true // !t returns false
A2 = !false // !f returns true

The data type of a programming element refers to what kind of data it can hold and how it stores that data. Data types apply to all values that can be stored in computer memory or participate in the evaluation of an expression. Every variable, literal, constant, enumeration, property, procedure parameter, procedure argument, and procedure return value has a data type. Programming element | Data type declaration | Variable | In a Dim Statement (Visual Basic)Dim amount As DoubleStatic yourName As StringPublic billsPaid As Decimal = 0 | Literal | With a literal type character; see "Literal Type Characters" in Type Characters (Visual Basic)Dim searchChar As Char = "." C | Constant | In a Const Statement (Visual Basic)Const modulus As Single = 4.17825F | Enumeration | In an Enum Statement (Visual Basic)Public Enum colors | Property | In a Property StatementProperty region() As String | Procedure parameter | In a Sub Statement (Visual Basic), Function Statement (Visual Basic), or Operator StatementSub addSale(ByVal amount As Double) | Procedure argument | In the calling code; each argument is a programming element that has already been declared, or an expression containing declared elementssubString = Left( inputString , 5 ) | Procedure return value | In a Function Statement (Visual Basic) or Operator StatementFunction convert(ByVal b As Byte) As String |

Numeric Data Type 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 | Length of string | 1 to 65,400 characters (fixed length) | str | strName | String | Length + 10 bytes | 0 to 2 billion characters (variable length) | str | strHTM4 | 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 | 16 bytes | Any value as large as Double (numeric) | vnt | vntNumber | Variant | Length+22 bytes | Same as variable-length string (text) | vnt | vntName |

EXAMPLE:

Dim X,Y As Int
X = (Int (txtbox1.text)
Y = (Int (txtbox2.text)
If X> Y Then Msgbox(X)
Else
Msgbox(Y)
EndIf