C language IV, typedef keyword, and scope

C language IV, typedef keyword, and scope one, typedef keywords

In the C language, there is a typedef keyword, the function of which is to allow you to define a new name for the type, that is, the individual name

For example:

　　

int DWORD

So later, when we define a variable of type unsigned int, this does not have to write unsigned int. Direct DWORD.

For example:

　　

DWORD name = 0;

Usually used in the definition of struct, and function pointer.

For example:

　　

typedef struct mystruct{   int A;   int b;    } Myintstruct;

Then the new type is myintstruct, and this type eliminates the keyword when you define it every time.

For example:

　　

int main{   //struct mystruct is;   Not defined before, to use the above   myintstruct is  ;   IS.A = ten;         return 0;  }

Ii. Scope

In the C language, the code you write has scope limitations.

What is the scope?

In short, when we define variables, this variable is accessed. To be accessible within a certain region.

For example, if you define variable a in the A function, and the B function defines the variable B, then the B function cannot use the A variable.

For example:

　　

#include <stdio.h>void  printfb () {   intone;    printf ("%d\r\n", b);   }       void PRINTFA () {  int;  printf ("%d\r\n", a);}

　　

The above is the function scope, that is, the {} block statement contains.

Code block scope:

The scope of a block of code is largely differentiated by {}.

For example:

　　

int main () {   int a = ten;   {      int a = one;      printf ("%d", a);    Block statement bracketing   }    printf ("%d", a);   return 0;}

If this is defined, then a is not redefined. and a = 11, after the code executes to the end. No longer exists.

File scope:

The file scope is defined outside the code. In other words, global variables. Global scope, which can be accessed at any location in the current file.

For example:

　　

　　

int a = ten;  Outside the declaration can be. int main () {   printf ("%d", a);   return 0;}

　　

C language IV, typedef keyword, and scope