The code `#ifndef CFIGURA_H` is a preprocessor directive in C...

The code #ifndef CFIGURA_H is a preprocessor directive in C or C++.

Explanation:

1. #ifndef stands for "if not defined".
2. The preprocessor checks whether the macro CFIGURA_H has been previously defined.
3. If CFIGURA_H has not been defined, the preprocessor includes the subsequent block of code (typically the contents of a header file).

Context:

This directive is commonly part of an include guard in a header file. Include guards prevent the same file from being included multiple times in a program, which can cause redefinition errors. For example, the code might look like this:

#ifndef CFIGURA_H
#define CFIGURA_H

// Contents of the header file go here

#endif // CFIGURA_H

How it works:

1. The first time the compiler includes the file, CFIGURA_H is not defined, so the block is processed, and CFIGURA_H is defined.
2. If the file is included again, CFIGURA_H is already defined, so the content inside the #ifndef ... #endif block is skipped.

This prevents issues like multiple inclusions of the same declarations or definitions, leading to errors such as "multiple definition" or "redefinition".