Typedef and typedef struct and # define

# Define n 100000

With this definition, using N in a program represents 100000.

Typedef int word4

Give the int A new name word4.

 

(Transfer)StructDifferences from typedef struct

It can be divided into three parts:
1 first: // Note that C and C ++ are different.
To define a struct type in C, use typedef:
Typedef struct student
{
Int;
} Stu;
So when declaring the variable, you can: Stu stu1; (if there is no typedef, you must use struct student stu1; to declare it)
The Stu here is actually the alias of struct student. Stu = struct student
In addition, student can also be left empty here (so it cannot be struct student stu1; it must be Stu stu1 ;)
Typedef struct
{
Int;
} Stu;
However, in C ++
Struct student
{
Int;
};
As a result, student of the struct type is defined, and student stu2 is directly used when the variable is declared;
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2. Second:
In C ++, if typedef is used, the following differences may occur:
Struct student 
{ 
Int; 
} Stu1 ;// Stu1 is a variable

 
Typedef struct student2 
{ 
Int; 
} Stu2;// Stu2 is a struct type = struct student

 
You can directly access stu1.a during use.
But stu2 must first stu2 S2;
Then s2.a = 10;
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Typedef and typedef struct and # define