A preprocessor directive that takes up more than one line needs a continuation symbol, nbackslash, as the very last character of every line except the last. Macros that are expanded into text are usually displayed to the user, but macros that are expanded into c code are executed with the rest of the c. They are used for turning on and off certain features. The c preprocessor and bitwise operations springerlink. Preprocessor directives in c 6 types of preprocessor. It is used include systemdefined and userdefined header files. C preprocessor c programming questions and answers page 3. A preprocessor is a program that examines c code before it is compiled and manipulates it in various ways. A c program basically consists of the following parts. Although the compiler doesnt have a separate preprocessor, the directives described in this section are processed as if there were one. Chapter 3 preprocessor directives abstract this chapter explains how c programs are processed in two distinct steps. Preprocessor directives can be used to access compiler or processor specific features. At times, however, you might want to compile only parts of your program depending on, for example, whether you are debugging or building your production code.
In chapter 4, table 43 presented a list of the c preprocessor directives supported by arduino c. C preprocessor c programming questions and answers page 1. These lines are only meaningful to the c preprocessor and never to the c compiler. The preprocessor complicates debugging, because the debugger sees the preprocessor output, not source code input. For example, the preprocessor can replace tokens in the text, insert the contents of other files into the source file, or suppress compilation of part of the file by removing sections of text. An introduction to c c programming language information. Types of preprocessor directives in c language trickyedu. Preprocessor directives in the examples youve seen so far, youve compiled your entire program whenever you compiled any of it.
The preprocessor phase also searches for special directives written by the programmer and converts them to code that can be handled by the compiler. Part of the springer books on professional computing book series sb computing. Directives in the source file tell the preprocessor to perform specific actions. This thesis describes a novel approach to preserve preprocessor directives.
Most c preprocessor features are inactive unless you give specific directives to request their use. The other is to define macros, which are names possibly with arguments that are expanded by the preprocessor into pieces of text or c code. In this chapter, we want to extend that discussion as well as cover a. Watch video to know about preprocessor commands in c language. Preprocessor directives are lines included in the code of our programs that are not program statements but. You use the following two preprocessor directives to define or undefine symbols for conditional compilation. The preprocessor is executed before the actual compilation of code begins, therefore the preprocessor digests all these directives. It must be the first nonblank character, and for readability, a preprocessor directive should begin in first column. This book covers various aspects of c programming including the. Apr 03, 2018 the preprocessor has the source file translation capabilities. It works on a linebyline basis, so the end of a line means something special to it. This tutorial explains about various preprocessors and macros. The behavior of the c preprocessor can be controlled and influenced using a set of directives. There are various directives in c, but some of them are very important especially the directives used for macro definition and the directives used for conditional compilation.
Only defined at the top of the program definition and only white space and comments may appear before preprocessor directive line. Preprocessor directives in c tutorial 18 october 2020. The rest of c thinks that endofline is little different from a space or tab character. The preprocessor provides the ability for the inclusion of header files, macro expansions, conditional compilation, and line control in many c implementations, it is a separate program invoked by the compiler as the first part of translation. The preprocessor do a quick read of the book section on the preprocessor. In the past, it has been abused as a general text processor. Whenever a cpp program is compiled then the following steps are taken.
The preprocessor is a utility program, which processes special instructions that can be or are written in a c cpp program. These c programming test with answers pdf cover all types of question asked in iift, xat, snap, gre, gmat, nmat, cmat, mat or for it companies written exam like wipro, hcl, infosys, accenture, government exams, ibps exams etc. It is one of the perfect c preprocessor e book pdf covering all types of questions in detail. A program needs c preprocessor directives to tell the compiler about, how to compile, what to include, what to add inline etc. Preprocessor arithmetic with extended integer types. This directive includes a copy of the specified file or library. The preprocessor provides the ability for the inclusion of header files, macro expansions, conditional compilation, and line control. Preprocessor directives are placed as the first lines of a program. One is to include external files, such as header files. In simplistic terms, a c preprocessor is just a text substitution tool and they instruct compiler to do required preprocessing before actual compilation. Its important to remember that the preprocessor is not working to the same rules as the rest of c.
Preprocessor directives can be used to maintain one code base for multiple program configurations. Preprocessor directives in c tutorial 18 october 2020 learn. The c preprocessor is a process before the compilation begins. The preprocessor stage and the preprocessor directives are the focus of this chapter. The preprocessor examines the code before actual compilation of code begins and resolves all these directives before any code is actually generated by regular statements.
This book provides a handson introductory course on concepts of c programming using a pic. The preprocessor doesnt know about the scope rules of c. 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. Preprocessor directives can make it easy to change key program characteristics. These lines are not program statements but directives for the preprocessor. The gnu c programming tutorial preprocessor directives. This manual discusses the gnu c preprocessor, the c. In this chapter, we want to extend that discussion as well as cover a few additional details that should prove useful to you. You can think of the c preprocessor as a separate program that runs before the compiler, with its own. The c preprocessor, often known as cpp, is a macro processor that is used automatically by the c compiler to transform your program before compilation. Covers topics like introduction to preprocessor directives, macro expansion, file inclusion, summary of preprocessor directives etc. Preprocessor lines are recognized and carried out before macro expansion.
The c preprocessor is not a part of the compiler, but is a separate step in the compilation process. Directives in the source file tell the preprocessor to take specific actions. Preprocessor identifiers are separate from regular c identifiers. C preprocessor directives tutorial to learn c preprocessor directives in simple, easy and step by step way with syntax, examples and notes. Using objectivec preprocessor directives techotopia. Pdf program refactoring in the presence of preprocessor directives. In many c implementations, it is a separate program invoked by the compiler as the first part of. Conditional compilation of program code or code segment. For example, the preprocessor can replace tokens in the text, insert the contents of other files into the source file, or suppress. Sass essentials is a fastpaced, handson guide that breaks down the mysteries of preprocessing css styles using the sass preprocessor and shows you how you can apply simple techniques to quickly and efficiently create css style sheets. Preprocessor directives are lines included in the code of. This page lists the preprocessor directives, or commands to the preprocessor.
Preprocessor directives preprocessor directives are lines included in the code of our programs that are not program statements but directives for the preprocessor. The c preprocessor is not part of the compiler but it extends the power of c programming language. The c preprocessor gcc, the gnu compiler collection. Following section lists down all important preprocessor directives. Preprocessor directives can be used to improve the readability of code. Gcc, the gnu compiler collection, contains a c preprocessor.
C programmingpreprocessor directives and macros wikibooks. Pdf the c preprocessor is heavily used in c programs because it provides. The c preprocessor directives are executed before the compilation of a program. The c preprocessor is not part of the compiler, but is a separate step in the compilation process. We have few more directives, which do not fit in the above categories, hence described separately. This book is a tutorial for the computer programming language c. It is called a macro processor because it allows you to definemacros, which are brief abbreviations for longer constructs. They are not regular code lines with expressions but indications for the compilers preprocessor.
1112 1355 253 530 128 147 902 775 1028 1243 425 942 960 865 106 156 159 1455 1180 1259 1081 368 1322 923 330 1235 883 796 1015 839 909 1178 1463 722 591