C++ #define

The C++ #define directive is used to define constants in a C++ program. It allows you to assign a name to a constant value, making it easier to use and understand in your code. Here are the steps to use the #define directive:

1. Start by writing the #define keyword, followed by the name you want to assign to the constant. For example, #define PI.

2. After the name, specify the value you want to assign to the constant. For example, #define PI 3.14159.

3. In your code, you can now use the defined constant by simply using its name. For example, if you defined PI as 3.14159, you can use it in your code like this: float circumference = 2 PI radius;.

4. You can also define constants with parameters. This allows you to create macros that can be used with different values. For example, #define MAX(a, b) ((a) > (b) ? (a) : (b)).

5. To undefine a constant, you can use the #undef directive followed by the name of the constant. For example, #undef PI.

By using the #define directive in C++, you can make your code more readable and maintainable by giving meaningful names to constant values.