Visual Basic Introduction

IDS 306from Shelly, Cashman & Repede

Microsoft Visual Basic 5: Complete Concepts and Techniques

Processing

• Parallel Processing -- more than one CPU (each with its own memory); able to carry out more than one instruction at a time

• Multitasking -- one processor, moves back and forth between programs

Graphical User Interface (GUI) Design

• Should be under user’s controluser should be able to customize

• Form should follow function

• Use concepts and metaphors familiar to user; parallel real-world experience

• Visually and functionally consistent

• Immediate feedback

• Attempt to prevent user mistakes

Program Development Life Cycle (PDLC)

Methodology -- organized plan that breaks process into steps

• Analyze the problem

• Design the problem

• Code the program

• Test and debug program

• Formalize solution

• Maintain the program

Hierarchical Input Process Output (HIPO) Chart

• A.k.a. hierarchy chart or top-down chart• Represents subdivision of activities visually• Lowest level instruction -- procedure

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Flow Chart• Process Symbol• Input/Output (I/O)• Flowline• Annotation• Decision• Terminal• Connector• Predefined Process

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Major Constructs of Structured Programming

• Control Structures– Sequence– Selection

• Case

– Repetition• Do…While

• Do…Until

Control Structures

• Sequence Control Structure -- used to show a single action or one action followed in order (sequentially by another)

• Selection Control Structure -- used to tell the program which action to take based on a certain condition

• Case Control Structure -- form of selection that allows for more than two alternatives

Control Structures (cont.)

• Repetition Control Structure -- a.k.a. looping or iteration; used when a set of actions is performed repeatedly– Do...While loop repeats as long as condition is true (may

never execute)– Do...Until loop evaluates condition at end of the loop

(will always execute at least once)

• Nested Control Structure -- contained within other control structures

Object-Oriented Programming (OOP)

• Object -- anything real or abstract, about which you store both data and operations that manipulate the data

• Class -- an implementation that can be used to create multiple objects with the same attributes and behavior

• Object is and Instance of a Class

Generalization Hierarchy

• Object-oriented design tool used to show the relationships among classes of objects

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Object-Oriented Terms

• Attribute -- identifying characteristics of individual objects, such as name or color

• Operation -- an activity that reads or manipulates the data of an object; called service in OOD, in OOP called a method

• Message -- has two parts: name of object to which message is sent, name of operation that will be performed. In OOP called event

Object Structure Diagram

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Event Diagram

• Used to represent relationships among events and operations

• Operations shown in rounded rectangles• Events shown on lines with arrows

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Major Constructs of OOP

• Encapsulation

• Inheritance

• Polymorphism

Encapsulation

• Capability of an object to have data (properties) and functionality (methods) available to the user without the user having to understand the implementation within the object

• Also called information hiding

• Process of hiding the implementation details of an object from its user

Inheritance

• A descendent class (subclass) that differs from its superclass in only one way contains just the code or data necessary to explain the difference

• Also known as subclassing

Polymorphism

• Allows an instruction to be given to an object in a generalized rather than specific detailed command

• Same command will get different but predictable results depending on object receiving command

• Specific actions, internal to object differ, results are the same

Rapid Application Development (RAD)

• Use of prebuilt objects to make program development much faster

• Shorter development life cycles

• Easier maintenance

• Capability to reuse components

Benefits of OOP

• Reusability -- classes designed to be reused in many systems or create modified classes using inheritance

• Stability -- classes designed for repeated reuse, become stable over time

• Easier Design -- object is a black box

• Faster Design -- can be created from existing components

Prototyping

• Process where developers iterate between refining the specifications and building working models of the system

Visual Basic

• Properties -- attributes of objects

• Controls -- check boxes, list boxes, etc.

• Forms -- windows that contain application’s controls

• Events -- messages or requests for service

• Procedures -- operations or services– include methods, functions, subroutines

Creating VB Applications

• Create the interface

• Set the properties

• Write the code