Hello World

 #include <iostream>
 
using namespace std;
 
int main() {
    cout << "Hello World!" << endl;
    return 0;
}

cout

Used to print something to the user screen.

  
 
 
 
 
    cout << "Hello World!" << endl;

'endl' is used to leave a blank line.

Both:

- #include <iostream>

- using namespace std;

are essentials to be able to use the cout.

 #include <iostream>
 
using namespace std;

Notes:

Operator	Meaning
+	Addition
-	Subtraction
*	Multiplication
/	Integer Division
%	Remainder after Division (Mod)

Note that the precedence of the multiplication is higher than that of the subtraction

 #include <iostream>
 
using namespace std;
 
int main() {
	cout << 500 - 100 * 4 << endl;
	return 0;
}

The Precedence of *, /, % is higher than that of +, -

 #include <iostream>
 
using namespace std;
 
int main() {
	int x = 10;
	cout << x << endl;
	return 0;
}

Reserves 4 bytes of memory to store integer values, calling these 4 bytes 'x' and giving 'x' an initial value = 10

  
 
 
 
 
	int x = 10;

If we declared a variable without giving it an initial value, the compiler gives it a random initial value.

 #include <iostream>
 
using namespace std;
 
int main() { 
    int x = 0;
    cin >> x;
    cout << x*x << endl;
}

Is used to take an input value and store it in a variable.

  
 
 
 
 
    
    cin >> x;

We can take more than one input value using only one 'cin':

 cin >> x >> y >> z;

Data Type	Description
int	Small integer number
double	Large real number
long long	Large integer number
string	A sequence of characters (word)
char	A single character
bool	Boolean number (0 or 1)