MS Visual Basic 6 Walter Milner VB 6

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 Tool. Box and drag in the form • Double click the new button to invoke the code editor Private Sub Command 1_Click() Msg. Box ("Hello world") End Sub • Enter code: • Click the Run button 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 – Active. X 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 Form 2 is a class Dim f As Form 2 Set f = New Form 2 f. Show f is an object – an instance of class Form 2 the Form 2 class has a method called show f. Back. Color = RGB(255, 0, 0) It has a property called Back. Color

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++