Introduction to C++

C++ is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significantly over time, and modern C++ now has object-oriented, generic, and functional features in addition to facilities for low-level memory manipulation.

Why Use C++

1.] C++ is one of the world's most popular programming languages.

2.] C++ can be found in today's operating systems, Graphical User Interfaces, and embedded systems.

3.] C++ is an object-oriented programming language which gives a clear structure to programs and allows code to be reused, lowering development costs.

4.] C++ is portable and can be used to develop applications that can be adapted to multiple platforms.

5.] C++ is fun and easy to learn!

6.] As C++ is close to C, C# and Java, it makes it easy for programmers to switch to C++ or vice versa.

C++ syntax

#include <iostream> using namespace std; int main()

{ cout << "Hello World!"; return 0; }

Example explained

Line 1: #include <iostream> is a header file library that lets us work with input and output objects, such as cout (used in line 5). Header files add functionality to C++ programs.

Line 2: using namespace std means that we can use names for objects and variables from the standard library.

Don't worry if you don't understand how #include <iostream> and using namespace std works. Just think of it as something that (almost) always appears in your program.

Line 3: A blank line. C++ ignores white space. But we use it to make the code more readable.

Line 4: Another thing that always appear in a C++ program, is int main(). This is called a function. Any code inside its curly brackets {} will be executed.

Line 5: cout (pronounced "see-out") is an object used together with the insertion operator (<<) to output/print text. In our example it will output "Hello World".

Note: Every C++ statement ends with a semicolon ;.

Note: The body of int main() could also been written as:
int main () { cout << "Hello World! "; return 0; }

Remember: The compiler ignores white spaces. However, multiple lines makes the code more readable.

Line 6: return 0 ends the main function.

Line 7: Do not forget to add the closing curly bracket } to actually end the main function.

C++ output

The cout object, together with the << operator, is used to output values/print text:

#include <iostream>
using namespace std;

int main()

{ cout << "Hello World!"; return 0; }

You can add as many cout objects as you want. However, note that it does not insert a new line at the end of the output

New Lines

To insert a new line, you can use the \n character:

#include <iostream>
using namespace std;
int main()

{ cout << "Hello World! \n"; cout << "I am learning C++"; return 0; }

Two \n characters after each other will create a blank line

Another way to insert a new line, is with the endl manipulator:

#include <iostream> using namespace std; int main()

{ cout << "Hello World!" << endl; cout << "I am learning C++"; return 0; }

C++ Variables

sVariables are containers for storing data values.

In C++, there are different types of variables (defined with different keywords), for example:

1.] int - stores integers (whole numbers), without decimals, such as 123 or -123

2.] double - stores floating point numbers, with decimals, such as 19.99 or -19.99

3.] char - stores single characters, such as 'a' or 'B'. Char values are surrounded by single quotes

4.] string - stores text, such as "Hello World". String values are surrounded by double quotes.

5.] bool- stores values with two states: true or false

Declaring (Creating) Variables

To create a variable, specify the type and assign it a value:

Syntax

type variableName = value;

Where type is one of C++ types (such as int), and variableName is the name of the variable (such as x or myName). The equal sign is used to assign values to the variable.

To create a variable that should store a number, look at the following example:

Example

Create a variable called myNum of type int and assign it the value 15:

int myNum = 15; cout << myNum;

Declare Many Variables

To declare more than one variable of the same type, use a comma-separated list:

Example

int x = 5, y = 6, z = 50;
cout << x + y + z;

One Value to Multiple Variables

You can also assign the same value to multiple variables in one line:

Example

int x, y, z;
x = y = z = 50;
cout << x + y + z;

C++ Strings

Strings are used for storing text.

A string variable contains a collection of characters surrounded by double quotes:

Example

Create a variable of type string and assign it a value:

string greeting = "Hello";

To use strings, you must include an additional header file in the source code, the <string> library:

Example

// Include the string library #include <string> // Create a string variable string greeting = "Hello";

C++ Loops

Loops can execute a block of code as long as a specified condition is reached.

Loops are handy because they save time, reduce errors, and they make code more readable.

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C++ While Loop

The while loop loops through a block of code as long as a specified condition is true:

Syntax

while (condition)

{ // code block to be executed }

In the example below, the code in the loop will run, over and over again, as long as a variable (i) is less than 5:

Example

int i = 0; while (i < 5) { cout << i << "\n"; i++; }

The Do/While Loop

The do/while loop is a variant of the while loop. This loop will execute the code block once, before checking if the condition is true, then it will repeat the loop as long as the condition is true.

Syntax

do { // code block to be executed } while (condition);

The example below uses a do/while loop. The loop will always be executed at least once, even if the condition is false, because the code block is executed before the condition is tested: