MS Visual Basic 6 Walter Milner

VB 6 0 Introduction –background to VB, A hello World program 1 Core language 1 –Projects, data types, variables, forms, controls, a calculator program 2 Core language 2 –Conditional statements, exception handling, loops, arrays, debugging 3 Core language 3 –Functions, sub-routines, parameter passing, modules, scope, lifetime 4 Controls –scrollbar, radio buttons, checkboxes, listboxes, timers, control arrays 5 Graphics –primitives and image files 6 Forms –Forms MDI, menus 7 Files and databases –adding controls, using data files, using databases 8 Deployment

Hello World in VB Start VB New Project – Standard.exe Click the Button control on the ToolBox and drag in the form Double click the new button to invoke the code editor Enter code: Click the Run button Private Sub Command1_Click() MsgBox ("Hello world") End Sub Exercise – try this out

What is Visual Basic? Kemeny and Kurtz – Dartmouth College 1964 For students – simple interpreted Many versions since MS VB versions – more power not so simple VBScript VBA.NET framework RAD especially of user interface

A very early version

VB is not.. Vendor independent Platform independent Based on a constant language definition Separated definition and IDE implementation Well documented (IMO) suitable for very large projects which must be maintained over a long period of time

VB is.. easy to use suitable for RAD very marketable

Building an application - steps Commercial – data driven – waterfall model – project management Science/engineering – underlying data and physical model, algorithms, testing In VB – RAD – focus on user interface prototyping and review.

Building an application - forms VB uses 'form' to mean Window Info on form stored in a.frm file VB system draws form based on that info Forms can be treated like classes in OOP - later

Building an application - controls Buttons, text boxes, labels, check boxes.. VB 'control' = user interface widget Some invisible – timer Controls have properties eg background color Three kinds – –standard –non-standard MS controls (common dialog, tab) and 3 rd party –ActiveX controls written in-house

Building an application - modularity Spaghetti programming, structured programming, OOP = increasing modularity In VB application constructed from modules = files in project- Form modules BASIC modules Class modules Private and public control interaction between modules

Building an application - objects Some OOP in VB – not pure OOP objects = things eg a form class = type of object eg a form design property = data value associated with object method = something the object can do

Building an application – example of OOP Dim f As Form2 Set f = New Form2 f.Show f.BackColor = RGB(255, 0, 0) Form2 is a class f is an object – an instance of class Form2 the Form2 class has a method called show It has a property called BackColor

Event-driven programming Standard approach for GUIs Contrast with old character interfaces – program determines what happens In GUI, the user triggers what application does (mostly) Event examples are key press, mouse move, timer timeouts Correspond to native Windows Messages (next slide) Event handler = a subroutine which will execute when that event happens

Windows Messages – Spy++