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Introduction

C++ is a programming language created by Bjarne Stroustrup and his team at Bell Laboratories in 1979. C++ is a general-purpose programming language that was developed as an enhancement of the C language to include object-oriented paradigm.

C++ is designed to be a compiled language, meaning that it is generally translated into machine language that can be understood directly by the system, making the generated program highly efficient. For that, a set of tools are needed, known as the development toolchain, whose core are a compiler and its linker.

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C++ is a middle-level language. It can be used to develop operating systems, browsers, games, and so on. C++ supports different ways of programming like procedural, object-oriented, functional, and so on. This makes C++ powerful as well as flexible. The basic syntax and code structure of both C and C++ are the same.

Features of C++

Applications of C++:

Basics of C++

Program Structure

C++, like most programming languages, runs line by line, from top to bottom. Here is the structure of a C++.

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First C++ Program – “Hello World!”

The “Hello World” program is the first step towards learning any programming language and is also one of the simplest programs you will learn. All you have to do is display the message “Hello World” on the screen. Let us now look at the program:

Program
// C++ program to display "Hello World"

// Header file for input output functions
#include <iostream>
using namespace std;

// Main() function: where the execution of program begins
int main()
{
	// prints hello world
	cout << "Hello World";

	return 0;
}
Output
Hello World!

Let us now understand every line and the terminologies of the above program:

  1. // C++ program to display “Hello World”: This line is a comment line. A comment is used to display additional information about the program. A comment does not contain any programming logic. When a comment is encountered by a compiler, the compiler simply skips that line of code. Any line beginning with // without quotes OR in between /*…*/ in C++ is comment.

  2. #include: In C++, all lines that start with pound (#) sign are called directives and are processed by a preprocessor which is a program invoked by the compiler. The #include directive tells the compiler to include a file and #include<iostream>. It tells the compiler to include the standard iostream file which contains declarations of all the standard input/output library functions.

  3. using namespace std: This is used to import the entirety of the std namespace into the current namespace of the program. The statement using namespace std is generally considered a bad practice. When we import a namespace we are essentially pulling all type definitions into the current scope. The std namespace is huge. The alternative to this statement is to specify the namespace to which the identifier belongs using the scope operator(::) each time we declare a type.

  4. int main(): This line is used to declare a function named main which returns data of integer type. A function is a group of statements that are designed to perform a specific task. Execution of every C++ program begins with the main()function, no matter where the function is located in the program. So, every C++ program must have a main() function.

  5. { and }: The opening braces { indicates the beginning of the main function and the closing braces } indicates the ending of the main function. Everything between these two comprises the body of the main function.

  6. std::cout«“Hello World!”;: This line tells the compiler to display the message Hello World! on the screen. This line is called a statement in C++. Every statement is meant to perform some task. A semi-colon ; is used to end a statement. Semi-colon character at the end of the statement is used to indicate that the statement is ending there. The std::cout is used to identify the standard character output device which is usually the desktop screen. Everything followed by the character << is displayed to the output device.

  7. return 0;: This is also a statement. This statement is used to return a value from a function and indicates the finishing of a function. This statement is basically used in functions to return the results of the operations performed by a function.

Character Sets in C++

The input and output of a program are made up of characters and symbols. C++ Character Set is a collection of characters and symbols that have a specified meaning. It consists of:

Tokens in C++

A token is the smallest unit of a program that the compiler understands. In C++, Tokens are divided into

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C++ Keywords

Keywords are predefined words that have special meanings to the compiler.

For example,

int money;

Here, int is a keyword that indicates money is a variable of type integer.

Here is a list of all C++ keywords. (as of C++17)

       
alignas decltype namespace struct
alignof default new switch
and delete noexcept template
and_eq do not this
asm double not_eq thread_local
auto dynamic_cast nullptr throw
bitand else operator true
bitor enum or try
bool explicit or_eq typedef
break export private typeid
case extern protected typename
catch false public union
char float register unsigned
char16_t for reinterpret_cast using
char32_t friend return virtual
class goto short void
compl if signed volatile
const inline sizeof wchar_t
constexpr int static while
const_cast long static_assert xor
continue mutable static_cast xor_eq

Note: As C++ is a case sensitive language, all keywords must be written in lowercase.

C++ Identifiers

Identifiers are the unique names given to variables, classes, functions, or other entities by the programmer. For example,

int money;
double accountBalance;

Here, money and accountBalance are identifiers.

Rules for naming identifiers
Examples of good and bad identifiers
Invalid Identifier Bad Identifier Good Identifier
Total points T_points totalPoint
1list list_1 list1
float n_float floatNumber

Constant

A constant, like a variable, is a memory location where a value can be stored. variables, constants never change in value. You must initialize a constant it is created.

Constant is declared with a const keyword whose value never changes in the execution of the program. The Fixed value is known as literals.

Constants-in-C

A constant is a token in C++ that corresponds to a number, character, or character string that can be used as a value in a program. Every constant has a type and a value on the basis of which, constants are categorised into the following types:

e.g.
const float f = 23.5f;

const double d = 34.6;

e.g.
const int a = 10;


e.g.
const char ch = 'A';


e.g.
const string str = "ABC";


#include <iostream>
int main()
{
   enum Days { Sunday, Monday, Tuesday,
            Wednesday, Thursday, Friday, Saturday };

   Days today;
   today = Monday;

   if (today == Sunday || today == Saturday)
      std::cout << "\nGotta' love the weekends!\n";
   else
      std::cout << "\nBack to work.\n";

   return 0;
}

Strings

Just like characters, strings in C++ are used to store letters and digits. Strings can be referred to as an array of characters as well as an individual data type.

It is enclosed within double quotes, unlike characters which are stored within single quotes. The termination of a string in C++ is represented by the null character, that is, \0. The size of a string is the number of individual characters it has.

In C++, a string can be declared in the following ways:

char name[30] = "Hello World!"; // The compiler reserves 30 bytes of memory for the string.

char name[] = "Hello World!"; // The compiler reserves the required amount of memory for the string.

char name[30] = { 'H' , 'e' , 'l' , 'l' , 'o', 'W', 'o', 'r','l','d','!'}; // This is how a string is represented as a set of characters.

string name = "Hello World"; // The compiler reserves 32 bytes of memory.

Special Symbols

Apart from letters and digits, there are some special characters in C++ which help you manipulate or perform data operations. Each special symbol has a specific meaning to the C++ compiler.

Here is a table which illustrates some of the special characters in C:

Special Character Trivial Name Function
[ ] Square brackets Used for single dimensional and multidimensional subscripts of arrays.
( ) Simple brackets Used for function calls and parameters.
{ } Curly braces Used to indicate the beginning and end of a code block.
, Comma Used to separate multiple statements like parameters in a function.
: Colon Used to invoke an initialization list.
; Semicolon used to mark the end of statements.
# Hash / Pound / Preprocessor The hash symbol represents a preprocessor directive used for denoting the use of a header file
* Asterisk We use the asterisk symbol in various respects such as to declare pointers, used as an operand for multiplication
~ Tilde We use the tilde symbol as a destructor to free memory
. Period / dot The use the dot operator to access a member of a structure

Operators

Operators are symbols that operate on operands. These operands can be variables or values. Operators help us to perform mathematical and logical computations.

We will see in-depth operators in next tutorial.

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