C Development Learning-structure type (enumeration/structure/type definition)

C Development Learning-structure type (enumeration/structure/type definition)
I. Enumeration definition: enumeration is a user-defined data type. The enum Enumeration type name used by the keyword is generally not used. It uses a name in braces, because they are constants, their types are int, and their values are from 0 to n. Enum colors {red, yellow, green} Syntax: enum Enumeration type name {name 0 m,..., name n };
Case 1: enumeration of automatic count

/// Main. c // enum /// Created by liuxinming on 15/4/26. // Copyright (c) 2015 liuxinming. All rights reserved. // # include
 
  
Enum COLOR {RED, YELLOW, GREEN, NumCOLORS}; int main (int argc, const char * argv []) {int color =-1; char * ColorNames [NumCOLORS] = {red, yellow, green}; char * colorName = NULL; printf (enter your preferred color code :); scanf (% d, & color ); if (color> = 0 & color <NumCOLORS) {colorName = ColorNames [color];} else {colorName = unknown;} printf (your preferred color is % s, colorName ); return 0 ;}
 

Case 2: You can specify the enum COLOR {RED = 1, YELLOW, GREEN = 5} when declaring the enumeration}
2. The structure is a combination of various variables consisting of basic data types and named by an identifier.
Different data types can be used in the structure.
Declarative Structure

Struct point {int x; int y;} struct point p1, p2; # Both p1 and p2 are point, which contains the values of x and y.

Struct {int x; int y;} p1, p2; # p1 and p2 are all untitled structures with values of x and y.

Structure Variable

Struct point p; # p is a structure variable p. x = 12; p. y = 20;

Case 1: use struct

/// Main. c // structure /// Created by liuxinming on 15/4/12. // Copyright (c) 2015 liuxinming. All rights reserved. // # include
 
  
// Declare the structure type struct date {int month; int day; int year ;}; int main (int argc, const char * argv []) {// Structure Variable & use struct date today; today. month = 04; today. day = 12; today. year = 2015; printf (Today is date is % I-% I ., today. year, today. month, today. day); return 0 ;}
 

Case 2: Structure Initialization

/// Main. c // structure /// Created by liuxinming on 15/4/12. // Copyright (c) 2015 liuxinming. All rights reserved. // # include
 
  
// Declare the structure type struct date {int month; int day; int year ;}; int main (int argc, const char * argv []) {struct date today = {04, 26,201 5}; struct date thismonty = {. month = 4 ,. year = 2015}; printf (Today is date is % I-% I ., today. year, today. month, today. day); printf (This month is % I-% I ., thismonty. year, thismonty. month, thismonty. day); return 0 ;}
 

Output:

Today is date is 2015-4-26.This month is 2015-4-0.

Structure member * the structure and array are a bit like [There are many units in the array, and many Members in the Structure * the array uses the [] Operator and subscript to access its member a [0] = 10; * structure. operator and name to access its member today. day structure operation * to access the entire structure, directly use the name of the Structure Variable * for the entire structure, you can assign a value, get the address, or pass it to the function parameter p1 = (struct point) {5, 10} // equivalent to p1.x = 5 p1.y = 10; p1 = p2; // equivalent to p1.x = p2.x; p1.y = p2.y;
The structure pointer * is different from the array. The structure variable name is not the address of the Structure Variable. You must use the & operator * struct date * pDate = & today;

/// Main. c // structure /// Created by liuxinming on 15/4/12. // Copyright (c) 2015 liuxinming. All rights reserved. // # include
 
  
// Declare the structure type struct date {int month; int day; int year ;}; int main (int argc, const char * argv []) {struct date today; today = (struct date) {04, 26,201 5}; struct date day; struct date * pDate = & today; printf (Today's date is % I-% I ., today. year, today. month, today. day); printf (The day's date is % I-% I ., day. year, day. month, day. day); printf (address of today is % p, pDate); return 0 ;}
 

Output:

Today's date is 2015-4-26.The day's date is 0-1606416456-32767.address of today is 0x7fff5fbff7f0Program ended with exit code: 0

The structure is used as the function parameter int numberOfDays (struct date d) * the entire structure can be passed into the function as the parameter value * at this time, a new structure variable is created in the function, copy the value of the caller's structure. * You can also return a Structure CASE: Enter today's date and output tomorrow's date. [This section describes the structure usage and does not describe the implementation process, I want to know about it myself]

/// Main. c // structure /// Created by liuxinming on 15/4/12. // Copyright (c) 2015 liuxinming. All rights reserved. // # include
 
  
# Include
  
   
// Declare the structure type struct date {int month; int day; int year ;}; bool isLeap (struct date d ); // judge whether it is a leap year int numberOfDays (struct date d); int main (int argc, const char * argv []) {struct date today, tomorrow; printf (Enter today's date (mm dd yyyy) :); scanf (% I, & today. month, & today. day, & today. year); if (today. day! = NumberOfDays (today) {tomorrow. day = today. day + 1; tomorrow. month = today. month; tomorrow. year = today. year;} else if (today. month = 12) {tomorrow. day = 1; tomorrow. month = 1; tomorrow. year = today. year + 1;} else {tomorrow. day = 1; tomorrow. month = today. month + 1; tomorrow. year = today. year;} printf (Tomorrow's date is % I-% I ., tomorrow. year, tomorrow. month, tomorrow. day); return 0;} int n UmberOfDays (struct date d) {int days; const int daysPerMonth [12] = {31,28, 31,30, 31,30, 31,31, 30,31, 30,31}; if (d. month = 2 & isLeap (d) {days = 29; // leap year} else {days = daysPerMonth [d. month-1];} return days;} bool isLeap (struct date d) {bool leap = false; if (d. year % 4 = 0 & d. year % 100! = 0) | d. year % 400 = 0) {leap = true;} return leap ;}
  
 

Output:

Enter today's date(mm dd yyyy):12 31 2014Tomorrow's date is 2015-1-1.Program ended with exit code: 0

Pointer to structure

struct date {  int month;  int day;  int year;} myday;struct date *p = &myday;(*p).month = 12;p->month = 12;

* Use-> to indicate the member in the structure variable to which the Pointer Points

/// Main. c // structure /// Created by liuxinming on 15/4/12. // Copyright (c) 2015 liuxinming. All rights reserved. // # include
 
  
Struct point {int x; int y ;}; struct point * getStruct (struct point *); void output (struct point); void print (const struct point * p ); int main (int argc, const char * argv []) {struct point y = {0, 0}; getStruct (& y); output (y ); output (* getStruct (& y); print (getStruct (& y); return 0;} struct point * getStruct (struct point * p) {scanf (% d, & p-> x); scanf (% d, & p-> y); printf (% d, % d, p-> x, p-> y ); return p;} void output (struct point p) {printf (% d, % d, p. x, p. y);} void print (const struct point * p) {printf (% d, % d, p-> x, p-> y );}
 

Output:

105010, 5010, 50

Structure Array

struct date dates[100];struct date dates[] = { {4,5,2005}, {2,4,2005}};

Case:

/// Main. c // structure /// Created by liuxinming on 15/4/12. // Copyright (c) 2015 liuxinming. All rights reserved. // # include
 
  
Struct time {int hour; int minutes; int seconds ;}; struct time timeUpdate (struct time now); int main (void) {struct time testTime [5] ={{ 11, 59, 59 },{, 0 },{, 29 },{, 59 },{, 27 }}; int I; for (I = 0; I <5; I ++) {printf (Time is %. 2i: %. 2i: %. 2i, testTime [I]. hour, testTime [I]. minutes, testTime [I]. seconds); testTime [I] = timeUpdate (testTime [I]); printf (... one second later it's %. 2i: %. 2i: %. 2i, testTime [I]. hour, testTime [I]. minutes, testTime [I]. seconds);} return 0;} struct time timeUpdate (struct time now) {++ now. seconds; if (now. seconds = 60) {now. seconds = 0; ++ now. minutes; if (now. minutes = 60) {now. minutes = 0; ++ now. hour; if (now. hour = 24) {now. hour = 0 ;}} return now ;}
 

Output:

Time is 11:59:59... one second later it's 12:00:00Time is 12:00:00... one second later it's 12:00:01Time is 01:29:29... one second later it's 01:29:30Time is 23:59:59... one second later it's 00:00:00Time is 19:12:27... one second later it's 19:12:28Program ended with exit code: 0

Structure

struct dateAndTime{  struct date sdate;  struct time stime;}

Nested Structure

Struct rectangle {struct point pt1; struct point pt2 ;}; // if there is a variable struct rectangle r; // You Can Have: r. pt1.x = 1; r. pt1.y = 2; r. pt2.x = 11; r. pt2.y = 22; // If a variable defines struct rectangle * rp; rp = & r; //, the four forms are equivalent. // r. pt1.x, rp-> pt1.x, (r. pt1 ). x, (rp-> pt1 ). x // but no rp-> pt1-> x because pt1 is not a pointer