The difference between C language typedef and #define

typedef和#define

define does not participate in compilation and is replaced during preprocessing .

typedefs participate in compilation and linking. Typedef is a rename, which can rename enum structures, etc., to improve code cleanliness.

First, the usage of typedef

In the C language, typedef is often used to define an alias for an identifier and a keyword. It is part of the language compilation process, but it does not actually allocate memory space. Examples are:

typedef    int       INT;
typedef   (int*)   pINT;

Typedef can enhance the readability of programs and the flexibility of identifiers, but it also has disadvantages such as "non-intuitiveness".

Second, the usage of define

define is a macro definition statement, which is usually used to define constants (including no parameters and with parameters), as well as to implement those macros that "seem to be kind on the surface, but behind a long list". It is not performed in the compilation process itself, but It is done before this (preprocessing process), but it is therefore difficult to find potential bugs and other code maintenance issues, examples of which are like:

define   FALSE        0
define   TRUE         1
define   Add(a,b)     ((a)+(b));
define   Loop_10      for (int i=0; i<10; i++)

3. The difference between typedef and #define

• #define belongs to the preprocessor, and typedef belongs to the compiler.
• #define is replacement, typedef is rename

Personal conclusion: both of these are rarely used