chapter 1 - a first program

8/7/2019 Chapter 1 - A First Program

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Microsoft Visual C# 2008

Comprehensive

Chapter 1A First Program Using C#


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Microsoft Visual C# 2008 Comprehensive 2

Objectives

Learn about programming

Explore object-oriented programming concepts

Learn about the C# programming language

Write a C# program that produces output

Learn how to select identifiers to use within yourprograms


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Objectives (continued)

Add comments to a C# program

Eliminate the reference to Out by using the System

namespace

Write and compile a C# program using the commandprompt and using Visual Studio

Learn alternate ways to write the Main() method


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Programming

Computerprogram Set of instructions that tells a computer what to do

Machine language

Expressed as a series of 1s and 0s 1s represent switches that are on, and 0s represent

switches that are off

High-level programming languages

Use reasonable terms such as read, write, or add Instead of the sequence of on/off switches that perform

these tasks


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Programming (continued)

High-level programming language (continued)

Allows you to assign reasonable names to areas ofcomputer memory

Has its own syntax (rules of the language) Compiler

Translates high-level language statements intomachine code

Programming logic Involves executing the various statements and

procedures in the correct order

To produce the desired results


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Programming (continued)

Debugging

Process of removing all syntax and logical errors fromthe program


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Object-Oriented Programming

Procedural program Create and name computer memory locations that

can hold values (variables)

Write a series of steps or operations to manipulatethose values

Identifier A one-word name used to reference a variable

P

rocedures ormethods Logical units that group individual operations used ina computer program

Called orinvoked by other procedures or methods


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Object-Oriented Programming(continued)

Object-oriented programming An extension of procedural programming

New features include: Objects Similar to concrete objects in the real world

Contain their own variables and methods

Attributes of an object represent its characteristics

State of an object is the collective value of all itsattributes at any point in time


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New features include (continued): Class

A category of objects or a type of object

Describes the attributes and methods of every objectthat is an instance, or example, of that class

Encapsulation

Technique of packaging an objects attributes and

methods into a cohesive unit That can be used as an undivided entity

Interface Interaction between a method and an object


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New features include (continued): Polymorphism

Describes the ability to create methods that actappropriately depending on the context

Inheritance

Provides the ability to extend a class to create a morespecific class


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The C# Programming Language

C# programming language

Developed as an object-oriented and component-

oriented language Part of Microsoft Visual Studio 2008

Allows every piece of data to be treated as an objectand to employ the principles of object-orientedprogramming

Contains a GUI interface that makes it similar toVisual Basic


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The C# Programming Language(continued)

C# programming language (continued)

Modeled after the C++ programming language

However, eliminates some of the most difficult featuresto understand in C++

Very similar to Java

In C# simple data types are objects


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Writing a C# Program that ProducesOutput

literal string

argumentsmethodobjectclassnamespace


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Writing a C# Program that ProducesOutput (continued)

Namespace

Provides a way to group similar classes

C# method parts Method header

Includes the method name and information about whatwill pass into and be returned from a method

Method body Contained within a pair of curly braces and includes all

the instructions executed by the method


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Writing a C# Program that ProducesOutput (continued)

Whitespace

Any combination of spaces, tabs, and carriage returns(blank lines)

Organizes your code and makes it easier to read

Keywords

Predefined and reserved identifiers that have specialmeaning to the compiler

Access modifier

Defines the circumstances under which the methodcan be accessed


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Selecting Identifiers

Requirements

Must begin with an underscore, at sign (@), or letter

Letters include foreign-alphabet letters Can contain only letters or digits

Not special characters such as #, $, or &

Cannot be a C# reserved keyword


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Selecting Identifiers (continued)


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Adding Comments to a Program

Program comments

Nonexecuting statements that document a program

Comment out

Turn a statement into a comment

Types of comments in C#

Line comments

Block comments XML-documentation format comments


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Adding Comments to a Program(continued)


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Eliminating the Reference to Out byUsing the System Namespace


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Eliminating the Reference to Out byUsing the System Namespace

(continued)


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Not Recommended: Using an Alias

using cannot be used with a class name

Alias

An alternative name for a class

Avoid using aliases if your intention is simply toreduce typing


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Not Recommended: Using an Alias(continued)


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Writing and Compiling a C# Program

Steps for viewing a program output

Compile source code into intermediate language(IL)

C#just in time (JIT) compiler translates theintermediate code into executable statements


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Compiling Code from the CommandPrompt

Command csc

Stands for C Sharp compiler


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Compiling Code from within the VisualStudio IDE

Advantages of using the Visual Studio IDE

Some of the code you need is already created for you

The code is displayed in color

You can double-click an error message and the cursorwill move to the line of code that contains the error

Other debugging tools are available


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Compiling Code from within the VisualStudio IDE (continued)


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Alternate Ways to Write a Main()

Method

Main() method with parameters


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Alternate Ways to Write a Main()

Method (continued)

Main() method with a return type


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You Do It

Enter your first C# program into a text editor so youcan execute it


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Entering a Program into an Editor

Use any text editor to write the following code andsave it as Hello.cs


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Compiling and Executing a Programfrom the Command Line

Type the command that compiles your program:

csc Hello.cs


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Compiling and Executing a Programfrom the Command Line (continued)

Execute the program Hello.exe


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Compiling and Executing a ProgramUsing the Visual Studio IDE

Steps

Create a new project (console application)

Enter the project name

Write your program using the editor

To compile the program, click Build on the menu bar,and then click Build Solution

As an alternative, you can press F6

Click Debug on the menu bar and then click StartWithout Debugging


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Compiling and Executing a ProgramUsing the Visual Studio IDE (continued)


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Compiling and Executing a ProgramUsing the Visual Studio IDE

(continued)


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Deciding which Method to Use

Advantage of using the command line

Saves disk space

Advantages of using the Visual Studio IDE

Automatic sentence completion

Words are displayed using different colors based ontheir category

Code automatically generated by the IDE is very

helpful when writing a GUI


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Adding Comments to a Program

Line comment example// Filename Hello.cs

// Written by

// Writtenon

Block comment example/* This programdemonstratestheuseof

the WriteLine()methodto printthe

message Hello, world!*/


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Summary

A computer program is a set of instructions that tella computer what to do

Procedural programming versus object-oriented

programming The C# programming language is an object-

oriented and component-oriented language

System.Console.Out.WriteLine() method

Produces a line of console output You can define a C# class or variable by using any

name or identifier


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Summary (continued)

Comments are nonexecuting statements that youadd to document a program

Or to disable statements when you test a program

Use of namespaces To create a C# program, you can use the Microsoft

Visual Studio environment

You have multiple options for writing the Main()

method header

chapter 1 - a first program

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