VB-1 Concepts

CIS241 - Fall 2001

 

v Control Constructs

       X If-Then  &  If-Then-Else

               VB is line oriented

               Demarcation via If, Then, Else, End If

       X While-Wend

               Continuation Test; PreTest

       X Do-Until

               Termination Test; PostTest

               Word Loop is required

       X For-Next

               Loop control variable (LCV, loop counter)

               Can specify increment (or decrement) with Step

               Non-integer values allowed for loop counter

       X Select-Case

               Concepts: ruling value expression, selection expression

               Case Else allowed

               Keywords: To, Is, End Select

 

v Subroutines

       X Event Procedures

                Name = <object>_<event>

                Template & parameters produced by IDE

                Invoked by occurrence of<event> with respect to <object>

                Code supplied by user

       X General Procedures

                Demarcation via Public/Private Sub, End Sub

       X Functions

                Demarcation via Public/Private Function, End Function

                Value returned by assignment to name of function

       X ByVal and ByRef parameters

               ByVal = pass by value

               ByRef = pass by reference

               Default is ByRef

 

 

 

v Interface Basics

       X IDE

               = integrated development environment

       X Main IDE components

               Title bar; Tool bar; Menu bar; Toolbox

               Project Design window

               Form Design window

               Project Explorer

               Properties Window

       X Some basic objects

               Form - where other objects are placed; project may have several

               Command button - main use: allow user to trigger subroutines

               Label - main use: display of information to user

               Textbox - main use: receive input from user

               Flexgrid - a grid of cells

       X Some basic properties

               Note: Different types of objects have the different sets of properties

               Name - the identifier used to reference the object in code

               Caption - What is seen on the screen

               Text - often the input typed by user; also what is displayed in the

                    cell of a FlexGrid

               Height, Width - determines size of object (in twips)

               Left, Top - determines placement of object with respect to its

                    container

               Backcolor, Forecolor - determines color of object and its caption

                    or text

               Font - determines size & type of font

 

v Data

       X Identifiers

               Used for: objects, variables, subroutines, etc.

       X Variables

               Can be local, module level, global, static

       X Types

               Integer, Long, Single, Double, etc.

       X Structures

               Arrays, user defined types (structures), arrays of objects