Chapter 1: Introduction to Visual Basic.NET: Background and Perspective Visual Basic.NET Programming: From Problem Analysis to Program Design

Chapter 1: Introduction to Visual Basic .NET:

Background and Perspective

Visual Basic .NET Programming:

From Problem Analysis to Program Design

Visual Basic .NET Programming: From Problem Analysis to Program Design 2

Objectives

• Learn basic computer terminology and component architecture

• Explore the history of programming languages

• Recognize the similarities between programming languages and spoken languages

• Solve problems and develop algorithms


Objectives (continued)

• Identify basic object-oriented programming concepts

• Examine the benefits of the object-oriented approach


Understanding Basic Computer Terminology And Component

Architecture

• Understand basic computer terms

• Fundamentals of how computer works

• Computer requires:

• Hardware

• Software



Architecture (continued)• Hardware

– Physical components of computer

• Architecture

– Arrangement of hardware components within computer




Architecture (continued)• Primary computer components:

– Input/output devices

– Memory

• Read-only memory (ROM)

• Random access memory (RAM)



Architecture (continued)

• Primary computer components (continued):

– Central processing unit

• Registers

• Arithmetic logic unit (ALU)

• Control unit

• Software

– Computer programs that are executed by hardware


Exploring the History of Programming Languages

• Modern programming languages

– Very powerful

– Enable you to develop sophisticated applications with relative ease

– Bear little resemblance to early counterparts

• HOWEVER, principal underpinnings remain unchanged


Machine Language

• Earliest programming languages• Consist of only 0’s and 1’s• Bit

– Binary digit of either 0 or 1– At machine level, computers only truly understand

bits

• Bit patterns– Used to represent other pieces of information

• Example: characters


Machine Language (continued)

• Memory location

– Can be represented as binary number using combination of bits



Assembly Language

• Provides one-to-one correspondence between each machine language instruction and a mnemonic

• Mnemonic

– Word or character string that represents an instruction

• Requires writing set of single-step instructions

• Easier for people to read and write


Assembly Language (continued)

• Sample instructions:

– CLR Clear the accumulator

– ADD A Add the contents of memory location A to the accumulator

– SUB G Subtract the contents of memory location G from the accumulator

– STO E Store the contents of the accumulator in memory location E


Assembly Language (continued)

• Assembler

– Translates mnemonics and memory location names into underlying machine code

• Program written for one computer architecture

– Usually will not run on different computer architecture

– Drawback of assembly language


High-level Languages

• Evolved due to needs for:

– Portability

– More expressive languages

• Easier to read, write, and maintain

• Less efficient in terms of:

– CPU time

– Memory


High-level Languages (continued)

• Compiler

– Translate program to machine code

• Linker

– Combines object code with other programs in class libraries

• Loader

– Loads object code into memory

– Executes program


High-level Languages (continued)

• Source code

– Program written by programmer

• Class library

– Collection of object files

– Support features and functions of a high-level language



Learning a Programming Language

• Understand basic vocabulary• Keywords

– Words built into language– Also called reserved words

• Statements– Consist of:

• Keywords

• Identifiers

• Symbols


Learning a Programming Language (continued)

• Procedures

– One or more related statements

– Work together to perform specific task

• Modules

– Self-sufficient group of related procedures

– Can combine with other modules to create applications



• Syntax

– Rules of language

– Includes:

• Spelling

• Punctuation

• Grammar

– Each programming language has own unique syntax and structure



• Syntax error

– Mistake in program

• Violates language rules

– Compiler checks for syntax errors


Learning a Programming Language

• Logic error

– Mistake in program

• Executes and produces incorrect result

– Also known as bugs

– Not checked by compiler


Solving Problems and Developing Algorithms

• Computer programming is problem solving

• Problems solved by programs

– Require inputs

– Produce outputs

• Algorithm

– Sequence of steps used to transform input(s) into desired output(s)




(continued)

• Critical that programmers embrace problem-solving approach

• Before writing code, programmer must:

– Understand problem at hand

– Properly identify inputs and outputs

– Develop transformation algorithm


Example 1-1: Creating a GPA Algorithm

Set TotalPoints,TotalHours, and GPA equal to 0

For each course

Get Grade and CreditHours

Add CreditHours to TotalHours

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


Example 1-1: Creating a GPA Algorithm (continued)

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



(continued)

• Desk-checking:

– Draw columns by hand that correspond to items in algorithm

– Create set of test data

– Step through algorithm

– Record changing values for each item


Example 1-2: Desk-Checking the Algorithm


Example 1-2: Desk-Checking the Algorithm (continued)


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



Concepts (continued)

• Object-oriented programming languages:– Becoming more popular

– Examples:• Java

• VB .NET

• Object – Thing that has characteristics 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 object 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




• 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 inheritance of methods


Examining the Benefits of the Object-oriented Approach

• Advantages:

– Naturalness

– Reusability

• OO approach still requires algorithm design:

– To define methods of object


Summary

• Computer consists of:

– Hardware

– Software

• Programming languages:

– Machine language

– Assembly language

– High-level languages


Summary (continued)

• 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

Documents

Chapter 1: Introduction to Visual Basic.NET: Background and Perspective Visual Basic.NET Programming: From Problem Analysis to Program Design