ABOUT VB 6.0

Introduction Visual Basic is a tool that allows you to develop Windows (Graphic User Interface – GUI) applications. The applications have a familiar appearance to the user. Visual Basic is event-driven; event driven meaning code remains idle until called upon to respond to some event (button pressing, menu selection). Visual Basic is governed by an event processor. The original Visual Basic for DOS and Visual Basic for Windows were introduced in 1991.  Steps in Developing Application There are three primary steps involved in building a Visual Basic application: 1. Draw the user interface 2. Assign properties to controls 3. Attach code to controls Rule for Variable Variables are used by Visual Basic to hold information.  No more than 40 characters  They may include letters, numbers, and underscore (_) The first character must be a letter You cannot use a reserved word (word needed by Visual Basic)  Visual Basic Data Types Data Type                               Suffix Boolean                                       None Integer                                         % Long (Integer)                            & Single (Floating)                         ! Double (Floating)                       # Currency                                      @ Date                                              None String                                            $ Variant                                         None Variable Declaration There are three ways for a variable to be typed (declared): 1. Default 2. Implicit 3. Explicit 1. Default variable in visual basic is variant, by default the variant data type is a special type used by Visual Basic that can contain numeric, string, or date data. 2. Implicit type a variable, use the corresponding suffix shown above in the data type table. For example, TextValue$ = "This is a string" creates a string variable, while Amount% = 300 creates an integer variable. 3. Explicit type a variable determines its scope. There are four levels of scope: a. Procedure level b. Global level Within a procedure & for Global, variables are declared using the Dim statement: Dim x as Integer Dim y as Double Dim name as String Visual Basic Operators           1.  arithmetic operator with  order of precedence are: Operator                Operation ^                                  Exponentiation *   /                              Multiplication and Division Mod                             Modulus +          -                      Addition and subtraction                  2. Comparison operators in Visual Basic: Operator                    Comparison >                                  Greater than <                                  Less than >=                                Greater than or equal to <=                                Less than or equal to =                                  Equal to <>                                Not equal to        3.  Logical operators Operator                    Operation Not                              Logical not And                              Logical and Or                                Logical or Message box The Message box displays a message, optional icon, and selected set of command buttons. The statement form of the message box returns no value (it simply displays the box): MsgBox Message, Type, Title where Message Text message to be displayed Type Type of message box (discussed in a bit) Title Text in title bar of message box Value                                     Meaning                                 Symbolic Constant 1                                              OK button selected                            vbOK 2                                              Cancel button selected                       vbCancel 3                                              Abort button selected                         vbAbort 4                                              Retry button selected                         vbRetry 5                                              Ignore button selected                        vbIgnore 6                                              Yes button selected                             vbYes 7                                              No button selected                              vbNo