Chapter 1B: Introduction to Visual Basic .NET: Background and Perspective

Software and s/w Development

Nov 18, 2013 (4 years and 5 months ago)

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CSIT 108

Fall 2007

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Chapter 1
B
: Introduction to Visual Basic .NET:

Background and Perspective

1.

Solving Problems and Developing Algorithms

Computer programming is problem solving

Problems solved by programs

Require inputs

Produce outputs

Algorithm

Sequence of steps used to t
ransform input(s) into desired output(s)

Critical that programmers embrace problem
-
solving approach

Before writing code, programmer must:

Understand problem at hand

Properly identify inputs and outputs

Develop transformation algorithm

Pseudo code

a short h
and way of describing a computer program. Rather than using the
specific syntax of a computer language, more general wording is used.
I
t is
easier for a non
-
programmer to unders
tand the general workings of a

program

tual programming language
.

Example 1
-
1: Creating a GPA Algorithm

(Credit Hours
: The amount of credit

that

students receive for completing a specific course)

Pseudo code:

Set TotalPoints,

TotalHours, and GPA equal to 0

For each course

If Grade is an ‘A’, multiply CreditHours by 4 and add result to TotalPoints

If Grade is a ‘B’, multiply CreditHours by 3 and add result to TotalPoints

If Grade is a ‘C’, multiply
CreditHours by 2 and add result to TotalPoints

If Grade is a ‘D’, multiply CreditHours by 1 and add result to TotalPoints

When no more courses

If TotalHours is not 0, calculate GPA = TotalPoints/TotalHours

Desk
-
checking:

Draw columns by hand that corres
pond to items in algorithm

Create set of test data

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Step through algorithm

Record changing values for each item

2.

Identifying Basic Object
-
oriented Programming Concepts

Procedural programming

Defining set of steps to transform

inputs into outputs

Translating steps into code

Object
-
oriented programming

Defining collection of objects that work together to solve problem

Object
-
oriented programming languages:

Becoming more popular

Examples:

Java

VB .NET

Object

Thing that has char
acteristics and behaviors

Attributes

Characteristics of an object

Methods

Behaviors of an object

Problem domain objects

Objects specific to problem being solved

Message

Asks object to invoke one of its methods

Encapsulation

Attributes and methods of obje
ct are packaged into single unit

Do not need to know internal structure of object to send messages to it

Class

Defines what all objects of group have in common

Instance

Specific member of group

Example:

Cheeseburger is an instance of food class

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Inheritance

Class of objects takes on characteristics of another class

Extends them as necessary

Subclasses

Superclass

Polymorphism

Different objects can respond in own way to same message

Related to inh
eritance of methods

CSIT 108

Fall 2007

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3.

Examining the Benefits of the Object
-
oriented Approach

Naturalness

Reusability

OO approach still requires algorithm design:

To define methods of object

Summary

Computers consists of:

Hardware

Software

Programming languag
es:

Machine language

Assembly language

High
-
level languages

Writing a program:

Understand problem

Develop algorithm

Desk
-
check

Write code

Object
-
oriented programming

Defines a collection of objects that work together to solve a problem