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
This article to share the content is detailed in the PHP constant: Define and const difference, has a certain reference value, the need for friends can refer to
A constant is a simple identifier. This value cannot be changed during script execution (in addition to the so-called magic constants, they are not constants). Constants are case sensitive by default. Usually, constant identifiers are always uppercase.
can be used
"Q" When defining constants in PHP, what is the difference between const and define?
The "answer" uses the const to make the code easy to read, and the const itself is a language structure, and define is a function. In addition, const is much faster to compile than define.
(1). Const is used to define a class member v
1. const is used for defining class member variables. once defined, the value cannot be changed. Define defines global constants that can be accessed anywhere. 2. define cannot be defined in the class, but const can. 3. const cannot define the constant if (...) {constFOO amp; #39;... SyntaxHigh in the condition statement.
1. const is used for defining class memb
# Ifndef # define # endif usage,
# Ifndef # define # endif usage
# Ifndef
# Ifndef in the header, which is critical. For example, you have two C files, both of which include the same header file. During compilation, these two C files need to be compiled into a runable file together, so the problem arises and a large number of declarations conflict.
Put the header file content in # ifndef and # endif. Wheth
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
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
Today continue to try the version of Seajs 2.3, then do something about the demo good, just a simple data template bar, and then through some other details in-depth study First look at the directory structure, according to the official demo erection Index.html is just a simple entry file and SEAJS configuration item, at the bottom there is a seajs.use load Crontroller module and then callback the exposed combine method Crontroller module, there are some official instructions and debugging, tri
[Convert] # ifndef # define # endif usage (Arrangement) Original Author: icwk
# Ifndef
# Ifndef in the header, which is critical. For example, you have two C files, both of which include the same header file. During compilation, these two C files need to be compiled into a runable file together, so the problem arises and a large number of declarations conflict.
Put the header file content in # ifndef and # endif. Whether or not your header file will b
Recently in the cloud Platform for the initial code architecture, encountered a constant definition speed comparison problem, so do a comparison.
The APC extension for PHP is described in the following paragraph in the PHP Manual:
http://cn.php.net/manual/zh/function.apc-define-constants.php
Define () is notoriously slow. Since the main benefit of APC is to increase the performance of scripts/applications,
The definition of APC constant is compared with define of PHP. Recently, when I was working on the preliminary code architecture of the cloud platform, I encountered a constant definition speed comparison problem, so I would like to make a comparison. Php apc extension, which is described in the following section in the PHP Manual: h recently encountered a constant definition speed comparison problem when working on the preliminary code architecture o
Use hidef extension in PHP instead of define to improve performance, hidefdefine. In PHP, hidef extension is used instead of define to improve performance. hidefdefine requires a new constant to open the local config. PHP file, think of hidef tested a few years ago and apc to improve PHP using hidef extension instead of define to improve performance, hidefdefine
A constant is a simple identifier. This value cannot be changed during script execution (in addition to the so-called magic constants, they are not constants). Constants are case sensitive by default. Usually, constant identifiers are always uppercase.
can be used define () function to define constants. After php5.3.0, you can use the Const keyword to define
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