Syntax and Basic Concepts

When learning any programming language, it is important to start with the basics. In this section, we will cover the basic syntax and concepts of C++. Understanding these fundamentals will lay the groundwork for more complex topics later on.

Variables

In C++, variables are used to store and manipulate data. Before using a variable, you must declare its type and give it a name. Here are examples of different types of variables:

• int: used to store integer values, such as 5 and -12
• double: used to store floating-point values, such as 3.14159 and 2.71828
• string: used to store sequences of characters, such as "Hello" and "World"

To declare a variable, you can use the following syntax:

1int x = 5;
2double pi = 3.14159;
3string name = "John";

In the above code, we declare three variables: x of type int with a value of 5, pi of type double with a value of 3.14159, and name of type string with a value of "John".

Output

In C++, the cout object is used to output information to the console. To output multiple values, you can use the << operator. Here is an example:

1int x = 5;
2double pi = 3.14159;
3string name = "John";
4
5cout << "Hello, " << name << "!" << endl;
6cout << "The value of x is: " << x << endl;
7cout << "The value of pi is: " << pi << endl;

The output of the above code will be:

1Hello, John!
2The value of x is: 5
3The value of pi is: 3.14159

Putting it Together

Let's put everything together and run a simple C++ program:

1#include <iostream>
2using namespace std;
3
4int main() {
5  int x = 5;
6  double pi = 3.14159;
7  string name = "John";
8
9  cout << "Hello, " << name << "!" << endl;
10  cout << "The value of x is: " << x << endl;
11  cout << "The value of pi is: " << pi << endl;
12
13  return 0;
14}

This program declares three variables (x, pi, and name), assigns them values, and then outputs them to the console using cout. When you run this program, you will see the following output:

1Hello, John!
2The value of x is: 5
3The value of pi is: 3.14159

xxxxxxxxxx

#include <iostream>

using namespace std;

​

int main() {

  int x = 5;

  double pi = 3.14159;

  string name = "John";

​

  cout << "Hello, " << name << "!" << endl;

  cout << "The value of x is: " << x << endl;

  cout << "The value of pi is: " << pi << endl;

​

  return 0;

}