Structure - C language

Why use a structure     

If the data you want to express is complex , It's not a value For example, you want to express the date   There are three values of month, year and day , If you want to express so many data gathered together as a whole    Then we need to use Structure

A structure is a composite data type

#include <stdio.h>
int main(int argc,char const *argv[])
{
    struct date {
    int month;
     int day;
      int year;
};
struct date toaay;
today. month = 07;
today.day = 31;
today .year = 2014;

printf( "Today's date is %i-%i-%i.\n",
today.year,today.month,today.day ) ;

return 0;
}

Within the function / Outside ?

And local variables — sample , The structure type declared inside the function can only be used inside the function
Therefore, the structure type is usually declared outside the function ,
In this way, it can be used by multiple functions

The form of the declaration structure

Three methods

struct point {
int x;
int y;};

struct point pl, p2;pl and p2 All are point     There are x and y Value
 

struct  {
int x;
int y;}     p1,p2  ;

p1 and p2 It's all a nameless structure , There are x and y

struct point {
int x;
int y;} pl, p2;

pl and p2 All are point     There are x and y Value

Initialization of structure

#include <stdio.h>
struct date {
int month;
int day;
int year;
};
int main(int argc, char const *argv[])
{
struct date today = {07,31,2014};                        \\ Assign values by 
struct date thismonth = {.month=7, .year=2014};           \\ Assign assignment 

printf("Today's date is %i-%i-%i.\n",
today. year,today.month,today.day ) ;
printf("This month is %i-%i-%i. ln",
thismonth.year,thismonth.month,thismonth.day ) ;
return 0;
}

Structural members

Structure and array are a bit like
Arrays use operators and subscripts to access their members a[0] =10;
For structure . Operators and names access their members

today.day            visit today The structure of the   day

p1.x                      visit p1 The structure of the x

Structural operations

To access the whole structure , Directly use the name of the structure variable for the whole structure , It can be assigned 、 Address fetch , It can also be passed to function parameters
pl = (struct point){5,I0}; amount to pl.x= 5;    pl.y = l0;

pl =p2;    amount to pl.x = p2.x; pl.y = p2.y;
Arrays can't do these two operations !