c语言第九章习题（C language ninth chapter exercises）.docVIP

c语言第九章习题（C language ninth chapter exercises） The ninth chapter: pretreatment Pretreatment Summary In the preceding chapter, has repeatedly used to command # at the beginning of the no.. If the # contains the command include command define # macrodefinition. In the source program, these commands are placed outside the function and are usually placed in front of the source file. They are referred to as preprocessing parts. Preprocessing refers to the work done prior to compiling the first scan (lexical scanning and syntax analysis). Preprocessing is an important function of the C language, which is handled by the preprocessing program. When compiling a source file, the system automatically references the preprocessing program, processes the preprocessing part of the source, and automatically enters the source code after processing. The C language provides a variety of preprocessing functions such as macro definition, file inclusion, conditional compilation, and so on. Programs that are properly written using preprocessing functions are easy to read, modify, transplant, and debug, and are also conducive to modular programming. This chapter describes several commonly used preprocessing functions. Macro definition In the C language source, it is allowed to represent a string with an identifier called macro. An identifier that is defined as a macro is called a macro name. When compiling the preprocessing, all occurrences of macro names in the program are replaced by strings defined in the macro definition. This is called macro substitution or macro expansion. A macro definition is done by the macro definition command in the source. Macro substitution is performed automatically by a preprocessing program. In C language, macro is divided into two types: parametric and non parametric. The definitions and calls of these two macros are discussed below. Macro definition without reference No macro name, no parameters after argument. The general form of the definition is: #define