The Preprocessor in C

The preprocessor is another unique feature of the c language that is generally not found in other high-level programming languages. the preprocessor provides a number of facilities to the programmer like.

• Program development process becomes easy.
• Simplifies modification in a program, reducing much agony.
• Portability of programs increases.
• Readability of program increases.
• Can develop efficient program easily.

The preprocessor program is a part of your turbo C compiler but as its name implies, it processes the source code before passing it to the compiler. This can be depicted as :

C source code

!

C source code after expansion

!

object code

!

executable code

The actions of the preprocessor are governed by preprocessor directives placed in the source file. A preprocessor directive always begins with the character # on a new line. It can be continue on the next line by using the backslash character.

Preprocessor directives can be classified into four categories:

1. Macro substitution directives.
2. File inclusion directives.
3. Conditional compilation directives.
4. Miscellaneous directives.

Programming books you should read !