Chapter 03 - Comments

COMMENTS

Program comments are explanatory statements that you can include in the C++ code that you write and helps anyone reading its source code. All programming languages allow for some form of comments. C++ supports single-line and multi-line comments. All characters available inside any comment are ignored by C++ compiler. 

C++ comments start with /* and end with */. For example:

/* This is a comment */ 
/* C++ comments can also 
* span multiple lines 
*/

A comment can also start with //, extending to the end of the line. For example:

#include<iostream> 
usingnamespace std;
main() 
{ cout <<"Hello World";
// prints Hello World 
return0; }

When the above code is compiled, it will ignore // prints Hello World and final executable will produce the following result:

HelloWorld

Within a /* and */ comment, // characters have no special meaning. Within a // comment, /* and */ have no special meaning. Thus, you can "nest" one kind of comment within the other kind. For example:

/* Comment out printing of Hello World:
cout << "Hello World"; 
// prints Hello World */

Chapter 02 - C++ Basic Syntax

C++ Basic Syntax 

When we consider a C++ program, it can be defined as a collection of objects that communicate via invoking each other's methods. Let us now briefly look into what do class, object, methods and instant variables mean. 

• Object - Objects have states and behaviors. Example: A dog has states - color, name, breed as well as behaviors - wagging, barking, eating. An object is an instance of a class. 
• Class - A class can be defined as a template/blueprint that describes the behaviors/states that object of its type support. 
• Methods - A method is basically a behavior. A class can contain many methods. It is in methods where the logics are written, data is manipulated and all the actions are executed. 
• Instant Variables - Each object has its unique set of instant variables. An object's state is created by the values assigned to these instant variables.

C++ Program Structure:

Let us look at a simple code that would print the words Hello World. 

#include<iostream> 

usingnamespace std; 

// main() is where program execution begins. 

int main() 

{ cout <<"Hello World";

// prints Hello World 

return0; }

Let us look various parts of the above program: 

• The C++ language defines several headers, which contain information that is either necessary or useful to your program. For this program, the header <iostream> is needed. 
• The line using namespace std; tells the compiler to use the std namespace. Namespaces are a relatively recent addition to C++. 
• The next line // main() is where program execution begins. is a single-line comment available in C++. Single-line comments begin with // and stop at the end of the line. 
• The line int main() is the main function where program execution begins.
• The next line cout << "This is my first C++ program."; causes the message "This is my first C++ program" to be displayed on the screen. 
• The next line return 0; terminates main( )function and causes it to return the value 0 to the calling process.

Complie & Execute C++ Program:

Let's look at how to save the file, compile and run the program. Please follow the steps given below:

• Open a text editor and add the code as above. 
• Save the file as: hello.cpp 
• Open a command prompt and go to the directory where you saved the file. 
• Type 'g++ hello.cpp' and press enter to compile your code. If there are no errors in your code, the command prompt will take you to the next line and would generate a.out executable file.
• Now, type ' a.out' to run your program. 
• You will be able to see ' Hello World ' printed on the window.

$ g++ hello.cpp 

$ ./a.out 

HelloWorld

Make sure that g++ is in your path and that you are running it in the directory containing file hello.cpp. You can compile C/C++ programs using makefile.

Semicolons & Blocks in C++:

In C++, the semicolon is a statement terminator. That is, each individual statement must be ended with a semicolon. It indicates the end of one logical entity.

For example, following are three different statements: 

x = y; 
y = y+1; 
add(x, y);

A block is a set of logically connected statements that are surrounded by opening and closing braces. For example:

{ cout <<"Hello World";  
// prints Hello World 
return0; }

C++ Identifiers: 

A C++ identifier is a name used to identify a variable, function, class, module, or any other user-defined item. An identifier starts with a letter A to Z or a to z or an underscore (_) followed by zero or more letters, underscores, and digits (0 to 9). C++ does not allow punctuation characters such as @, $, and % within identifiers. C++ is a case-sensitive programming language. Thus, Manpower and manpower are two different identifiers in C++.

C++ Keywords:

The following list shows the reserved words in C++. These reserved words may not be used as constant or variable or any other identifier names.

WhiteSpace in C++:

A line containing only whitespace, possibly with a comment, is known as a blank line, and C++ compiler totally ignores it. Whitespace is the term used in C++ to describe blanks, tabs, newline characters and comments. Whitespace separates one part of a statement from another and enables the compiler to identify where one element in a statement, such as int, ends and the next element begins. Therefore, in the statement,

Chapter 01 - Overview

Overview

C++ is a statically typed, compiled, general-purpose, case-sensitive, free-form programming language that supports procedural, object-oriented, and generic programming. C++ is regarded as a middle-level language, as it comprises a combination of both high-level and low-level language features. C++ was developed by Bjarne Stroustrup starting in 1979 at Bell Labs in Murray Hill, New Jersey, as an enhancement to the C language and originally named C with Classes but later it was renamed C++ in 1983. C++ is a superset of C, and that virtually any legal C program is a legal C++ program. Note: A programming language is said to use static typing when type checking is performed during compile-time as opposed to run-time.

Object Oriented Programming: 

C++ fully supports object-oriented programming, including the four pillars of object-oriented development: 

• Encapsulation 
• Data hiding 
• Inheritance 
• Polymorphism

Standard Libraries:

Standard C++ consists of three important parts: 

• The core language giving all the building blocks including variables, data types and literals, etc. 
• The C++ Standard Library giving a rich set of functions manipulating files, strings, etc.
• The Standard Template Library (STL) giving a rich set of methods manipulating data structures, etc.

The ANSI Standard:

The ANSI standard is an attempt to ensure that C++ is portable -- that code you write for Microsoft's compiler will compile without errors, using a compiler on a Mac, UNIX, a Windows box, or an Alpha. The ANSI standard has been stable for a while, and all the major C++ compiler manufacturers support the ANSI standard.

Learning C++:

The most important thing to do when learning C++ is to focus on concepts and not get lost in language technical details. The purpose of learning a programming language is to become a better programmer; that is, to become more effective at designing and implementing new systems and at maintaining old ones. C++ supports a variety of programming styles. You can write in the style of Fortran, C, Smalltalk, etc., in any language. Each style can achieve its aims effectively while maintaining runtime and space efficiency.

Use of C++:

C++ is used by hundreds of thousands of programmers in essentially every application domain. C++ is being highly used to write device drivers and other softwares that rely on direct manipulation of hardware under realtime constraints. C++ is widely used for teaching and research because it is clean enough for successful teaching of basic concepts. Anyone who has used either an Apple Macintosh or a PC running Windows has indirectly used C++ because the primary user interfaces of these systems are written in C++.