c程序中的宏定义及运用（Macro definition and application in C program）.docVIP

c程序中的宏定义及运用（Macro definition and application in C program） C language macro definition (translation) C language 2010-03-20 15:09:14 read 174 comment 0: big and small Define is the C language macro definition commands, its main purpose is to provide a convenient programmer in programming, and can improve the efficiency of the program to a certain extent, but the students often do not understand the nature of the order, always have some confusion here, misuse of the order in the programming. The purpose of the program is expected to run and is not the same, or reading someone else to write the program, the operation results to understand the error, which is detrimental to the C language learning. 1 #define command profiling The concept of 1.1 #define The #define command is a macro definition command in the C language that defines an identifier as a string that is called a macro name and the defined string is called an alternate text. The command comes in two formats: one is a simple macro definition, and the other is a macro definition with arguments. (1) a simple macro definition: #define name string Example: #define PI 3.1415926 (2) macro definition with parameters #define macro ( parameter table ) macro body Example: #define A (x) x When an identifier is defined by a macro, the identifier is a macro name. At this point, the macro name appears in the program. Before the program is compiled, the macro name is replaced by the defined string, which is called macro substitution, which is compiled after substitution, and macro substitution is a simple replacement. 1.2 timing of macro substitution To really understand the role of #define, lets take a look at the processing of the C language source program. When we compile a good source code in an integrated development environment, such as Turbo C, we actually do some preprocessing, compiling, assembling, and linking, as shown in figure 1. source program Preprocessor The modified source program Compiler Assembler