define paas

#ifndef#define#endif的用法#ifndef#define#endif的用法  你所遇到的这几个宏是为了进行条件编译。一般情况下，源程序中所有的行都参加编译。但是有时希望对其中一部分内容只在满足一定条件才进行编译，也就是对一部分内容指定编译的条件，这就是“条件编译”。有时，希望当满足某条件时对一组语句进行编译，而当条件不满足时则编译另一组语句。     条件编译命令最常见的形式为：     #ifdef 标识符     程序段1     #else     程序段2     #endif         它的作用是：当标识符已经被定义过(一般是用#define命令定义)，则对程序段1进行编译，否则编译程序段2。     其中#else部分也可以没有，即：     #ifdef     程序段1     #

Difference between typedef and define The following code is used to describe Typedef char * typedef_char;# Define define_char char * // No semicolon here Void main (INT argc, char * argv []){Char s [] = "ASDF ";Const typedef_char P = s; // char * const* P = 'B'; // The P pointer is a constant pointer. It cannot point to anything else, but the content to which it points can be changed. Cout Const define_c

In general, we define a constant using # define, #define的本质是文本替换, for example, # define INT_PTR int*, when we use a int_ptr,int_ptr a, B, which is equivalent to an INT * A, A, a, b; That is, define a pointer variable A and integer variable B, which is a common scenario for #

1 NO parameter macro definitionThe macro name of the parameterless macro is not followed by a parameter.The general form of its definition is:#define Identifier stringWhere the "#" indicates that this is a preprocessing command. All that begin with "#" are pre-processing commands. "Define" defines the command for the macro. "Identifier" is the name of the macro defined. A "string" can be a constant, an expr

Note: Define cannot be defined in a class, and the const must be defined in a class, and the const must be accessed by the class name:: Variable name 1. Const is used for class member variable definition once defined and cannot change its value. Define defines global constants that can be accessed anywhere.2, define can not be defined in the class and Const.3. C

1) #define是预处理指令, in the compilation preprocessing simple substitution, does not make the correctness check, does not have the meaning whether correctly still to carry in, only has in the compilation has been expanded the source program only then discovers the possible error and errors. Like what:#define PI 3.1415926In the program: Area=pi*r*r will be replaced with 3.1415926*r*rSuppose you write the number

1) #define是预处理指令, in the compilation preprocessing simple substitution, does not make the correctness check, does not have the meaning whether correctly still brings in, only when compiles the already expanded source program only then discovers the possible error and error. For example:#define PI 3.1415926In the program: Area=pi*r*r will be replaced with 3.1415926*r*rIf you write the number 9 in the #

Define is a pre-processing command in C language. It is used for macro definition, which can improve the readability of the source code and provide convenience for programming. Pre-processing commands start with "#", for example, include commands # include and macro-defined commands # define. Usually put in front of the source file, which is called preprocessing. Preprocessing refers to the work done before

1 :__ file __,__ line __, macro expanded, Middle Layer Macro _ File _ is the predefine macro of the compiler, indicating the absolute path of the file, but ASCII characters. Suppose you want to convert _ file _ into a wide character. Maybe you want # DEFINE _ wfile _ L ##__ file __ Wchar_t pszfilepath [] =__ wfile __; In this case, the compiler will prompt that "l1_file _" is an undeclared identifier. Why? If the parameter after # Is a macro, # will

Original article address: Http://blog.csdn.net/kindazrael/article/details/8108868 In C, Preprocessor is a powerful tool that makes your code easier to read and modify. With preprocessing code, you can redefine a part of the code to make your code more suitable for your style. Preprocessor is processed in advance before the code is compiled. The pre-processing code starts with a pound sign.1. About #define #defineDeclarations are mainly used to assign

#define宏定义在C系开发中可以说占有举足轻重的作用. The underlying framework does not have to say, in order to compile optimization and convenience, as well as cross-platform capabilities, macros are heavily used, it can be said that the bottom of development left define will be unable to move. When developing at a higher level, we put more emphasis on business logic and seem to have little use and reliance on macros.But the ben

Reference:typedef usage Http://www.cnblogs.com/ggjucheng/archive/2011/12/27/2303238.html#define用法: http://blog.csdn.net/benny5609/article/details/2314541====typedef=====There are generally two uses for typedef: one is to give the variable a new name that is easy to remember and makes sense, and the other is to simplify some of the more complex type declarations.egtypedef int size;typedef unsigned int WORD;typedef with arrays, pointersGeneral Array Dec

Original address: http://www.manongjc.com/article/491.html Const is the definition of a class member constant, which cannot be changed after the definition, and define we define global constants so that we can access them elsewhere but not change them. Note: Define cannot be defined in a class, and a const must be defined in a class, and the const must be access

// ================================================ ========================================// Title:// How to Write elegant code (2) -- # define? Const? Or enum?// Author:// Norains// Date:/// Tuesday 21-July-2009// Environment:// Wince5.0 + vs2005// ================================================ ======================================== # Define, const, and Enum: What are the associations between the thr

1. Simple macro definition #define Identifier substitution list (alternate list can be number, string literal, punctuation, operator, identifier, keyword, Word constants quantity.) Note: The substitution list is nullable. Typical error: #define N = 100 int a[n]; /* This will become an int a[= 100], which will be processed as an identification mark. #define N

# Define is a macro definition Command provided in C language. Its main purpose is to provide programmers with some convenience in programming and improve the program running efficiency to a certain extent, however, when learning this command, you often cannot understand the essence of the command, and there is always some confusion here. The command is misused during programming, so that the running of the program is inconsistent with the expected pu

1. Define a simple constant: Define a constant to facilitate modification. (do not add a semicolon to the end !) # Define n 1000 It is equivalent to const int n = 1000, but slightly different. Define is a simple replacement instead of a quantity. 2. Define simple functions:

1. Simple define Definition# Define maxtime1000A simple maxtime is defined. It represents 1000. If you writeIf (I The compiler replaces maxtime with 1000 before processing this code.This definition looks similar to a normal constant definition const, but it is also different, because the definition of define is more like a simple text replacement, rather than bei

Original article address: Http://blog.csdn.net/kindazrael/article/details/8108868 Objective-C: # define Usage Analysis In C, Preprocessor is a powerful tool that makes your code easier to read and modify. With preprocessing code, you can redefine a part of the code to make your code more suitable for your style. Preprocessor is processed in advance before the code is compiled. The pre-processing code starts with a pound sign.1. About #

Asynchronous modules define AMD and asynchronous modules amd It is called Asynchronous Module Definition, and is defined by Asynchronous components (or modules. AMD is a mechanism in which components and their dependencies can be asynchronously loaded.Define Method define(id?, dependencies?, factory); Component ID The component ID is the unique identifier of a component. In a script file that is one-to-one