What is the purpose of the #define directive in programming languages like C and C++?

The #define directive in C and C++ is a preprocessor command used to define macros. Macros can be constants or code snippets that are substituted into the program wherever they are referenced. For example, #define PI 3.14 defines a constant named PI with the value 3.14 . Similarly, #define SQUARE(x) ((x) * (x)) defines a macro for computing the square of a number. This directive helps in making the code more readable, manageable, and easier to maintain by avoiding the repetition of constants and code fragments. It operates at the preprocessing stage before the actual compilation of the code begins.