Basics

A Very Basic C++ Program

```cpp basic_program.cpp

include

using namespace std;

int main() { string name;

cout<<"Enter your name : ";
getline(cin, name);

cout<<"Hello "<<name;

return 0;

} ```

Variables

• Variables are containers for storing data values.
• Syntax : type variableName = value;
• int number = 8 here number is a variable.
• int x = 5, y = 6, z = 50;

Identifiers

• All variables must be identified with unique names.
• These unique names are called identifiers.
• Names are case sensitive (myVar and myvar are different variables)

Constants

• When we do not want to change existing variable values, we use the const keyword.
• This will declare the variable as "constant", which means unchangeable and read-only.
  • const int myNum = 15; // myNum will always be 15
  • myNum = 10; // error: assignment of read-only variable 'myNum'
• When we declare a constant variable, it must be assigned with a value, not like this :
  • const int minutesPerHour;
  • minutesPerHour = 60; // error

Comments

• Comments can be used to explain C++ code, and to make it more readable.

• Comments can be singled-lined or multi-lined.

  Single-line Comments :

  • Single-line comments start with two forward slashes (//).
  • Any text between // and the end of the line is ignored by the compiler (will not be executed).
  • // This is a comment

  Multi-line Comments :

  • Multi-line comments start with / and ends with /.
  • Any text between / and / will be ignored by the compiler:
  • For example : cpp /* The code below will print the words Hello World! to the screen, and it is amazing */ cout << "Hello World!";

User Input

• We can use cin to get user input.
• cin is a predefined variable that reads data. cin is pronounced "see-in". Used for input, and uses the extraction operator (>>)
• For example : cpp int x; cout << "Type a number: "; // Type a number and press enter cin >> x; // Get user input from the keyboard cout << "Your number is: " << x; // Display the input value
• cout is pronounced "see-out". Used for output, and uses the insertion operator (<<)