C programming preprocessor directives trytoprogram. Before the actual compilation of every c program it is. This section contains solved programs of c preprocessor directives. It is possible for a c program to print the currently executing line of source code, the file of the source code, and the name of the current function.
It expands macros in parts of some directives that arent skipped as part of a conditional compilation. The output is said to be a preprocessed form of the input data, which is often used by some subsequent programs like compilers. Preprocessor directives c programming developer insider. To count as a word, foo cant be adjacent to other alphanumeric characters, so for example food will not expand to 12d. Nested preprocessor macro directive having arguments in c. Here is the universally acclaimed hello world program without main. These are macros having arguments every time whenever the macro name is encountered, the arguments are replaced by the actual arguments from the program. For example in the following program max is defined as 100. It is called a macro processor because it allows yo u to define macros, which are brief abbreviations for longer constructs. In simple terms, a c preprocessor is just a text substitution tool and it instructs the compiler to do required preprocessing before the actual compilation. When we try to compile a program, preprocessor commands are executed first and then the program gets compiled.
It is called a macro processor because it allows you to define macros, which are brief abbreviations for longer constructs the c preprocessor provides four separate facilities that you can use as you see fit. Covers topics like introduction to preprocessor directives, macro expansion, file inclusion, summary of preprocessor directives etc. We can pl ace these preproce ssor directives anyw here in our pro gram. Therefore, you cannot create a comment by concatenating and. When we write a c program, we will use some of the header files and macros. Preprocessors are a way of making text processing with your c program before they are actually compiled. The line macron, a, i, m is again replaced by main. The quiz contains multiple choice and output questions for interview gate preparation. C programmingpreprocessor directives and macros wikibooks. C preprocessor directives tutorial to learn c preprocessor directives in simple, easy and step by step way with syntax, examples and notes. Whenever the name is used, it is replaced by the contents of the macro. These transformations can be the inclusion of header file, macro expansions etc. The c preprocessor is not a part of the compiler, but is a separate step in the compilation process.
Preprocessor directives in c programming language are used to define and replace tokens in the text and also used to insert the contents of other files into the source file. In this article, we will explore preprocessor directives in c programming. In many c implementation s, it i s a separ ate program invoked by the compiler as the first part of translation. Macros the c preprocessor gcc, the gnu compiler collection. The c preproces sor i s a m acro processor that is used automatically b y t he c compiler to transfo rm your p rogram before actual compila tion propro cessor direcives are executed before compilation. The c preprocessor modifies a source code file before handing it over to the. Keep in mind that th e c preprocess or converts comments to whitespace b efore macr os are even considered.
And dealing with them is inevitable in c programming. The c preprocess or is not a part of the compiler, but is a separate step in the compilation process. Before a c program is compiled in a compiler, source code is processed by a program called preprocessor. They differ mostly in what they look like when they are used. As with stringizing, the actual argument is not macro expanded first. Macro name within another macro is called nesting of macro. The c preprocessor modifies a source code file before handing it over to the compiler. It is also called as simple substitution macro as it simply removes the occurrences of the constant and replace them using the expression. In simple terms, a c preproce ssor is just a text substitution tool and it instructs the compiler to do requi red preproces sing before the actual compilation. The amount and kind of processing done depends on the nature of the preprocessor. The pr eprocessor provides the ability for the inclusion o f hea d er fil es, macro expansions, conditional compilation, and line control. A macro is a fragment of code which has been given a name.
Apart from macros, there are other preprocessor directives which are pretty useful as. The c preprocessor is a macro processor that is used automatically by the c compiler to transform your program before actual compilation proprocessor. Preprocessor processes our program before going to the compiler. The program has a preprocessor that replaces main with macron, a, i, m. Preprocessor programs provide preprocessors directives which tell the compiler to preprocess the source code before compiling. Below is the list of preprocessor directives that c programming language. The c p reproc essor is a macro preprocessor allow s you to define macros tha t transfor ms your program before it is compiled. Many of write c program without knowing what actually preprocessor is. In computer science, a preprocessor is a program that processes its input data to produce output that is used as input to another program. How to check whether a macro is defined or not in c. Interesting facts about macros and preprocessors in c. Here, we will learn all about c language preprocessor operators, directives through examples.