[Study Notes] [C Language] structure, Study Notes C Language

[Study Notes] [C Language] structure, Study Notes C Language

1. Three Methods for defining struct Variables
1> first define the type, then define the variable (separate definition)
Struct Student
{
Int age;
};
Struct Student stu;
 
2> define both types and variables
Struct Student
{
Int age;
} Stu;
Struct Student stu2;
 
3> define a variable while defining the type (the type name is omitted)
Struct
{
Int age;
} Stu;
 
2. struct type Scope
1> defined outside the function: globally valid (starting from the row of the definition type to the end of the file)
2> defined within a function (code block): the code block is partially valid (starting from the row of the definition type until the end of the code block)

3. Code

1> struct

1/* 2 array: it can only consist of multiple data of the same type 3 4 struct: It can consist of multiple different types of data 5 */6 # include <stdio. h> 7 8 int main () 9 {10 // int ages [3] = {[2] = 10, 11, 27 }; 11 12 13 // int ages [3] = {10, 11, 29}; 14 15 // 1. define the struct type 16 struct Person17 {// The three variables in it, which can be called the struct member or attribute 18 int age; // age 19 double height; // height 20 char * name; // name 21}; 22 23 // 2. according to the struct type, the struct variable 24 struct Person p = {20, 1.55, "jack"}; 25 p. age = 30; 26 p. name = "rose"; 27 28 printf ("age = % d, name = % s, height = % f \ n", p. age, p. name, p. height); 29 30/* incorrect syntax 31 struct Person p2; 32 p2 = {30, 1.67, "jake"}; 33 */34 35 struct Person p2 = {. height = 1.78 ,. name = "jim ",. age = 30}; 36 // p2.age = 25; 37 38 return 0; 39}

2> structure memory Analysis

1 # include <stdio. h> 2 int main () 3 {4 5 6 return 0; 7} 8 9 // Complement Algorithm 10 void test1 () 11 {12 struct Student13 {14 int age; // 4 bytes 15 16 char a; 17 18 // char * name; // 8 bytes 19}; 20 21 struct Student stu; 22 // stu. age = 20; 23 // stu. name = "jack"; 24 // complement the algorithm (alignment algorithm) 25 // the storage space occupied by the struct must be a multiple of the maximum number of member bytes 26 27 int s = sizeof (stu); 28 printf ("% d \ n", s ); 29} 30 31 // struct memory details 32 void test () 33 {34 // 1. define struct type (no storage space is allocated) 35 struct Date36 {37 int year; 38 int month; 39 int day; 40}; 41 42 // 2. define struct variables (actually allocating buckets) 43 struct Date d1 = {2011, 4, 10}; 44 45 46 struct Date d2 = {2012, 8, 9 }; 47 48 // values of all d1 members are assigned to all d2 members 49 d2 = d1; 50 d2.year = 2010; 51 52 printf ("% d-% d \ n", d1.year, d1.month, d1.day ); 53 54 printf ("% d-% d \ n", d2.year, d2.month, d2.day ); 55/* 56 printf ("% p-% p \ n", & d1.year, & d1.month, & d1.day); 57 58 int s = sizeof (d1 ); 59 printf ("% d \ n", s); 60 61 */62}

3> Notes

1 # include <stdio. h> 2 // from the beginning of this line to the end of the file, it is valid (like the global variable) 3 struct Date 4 {5 int year; 6 int month; 7 int day; 8}; 9 10 int a; 11 12 void test2 () 13 {14 struct Date 15 {16 int year; 17 }; 18 // here we use the struct Date type 19 struct Date d1 = {2011} inside the test2 function; 20 21 22 // The struct type is also available, from the row that defines the type to the end of the code block 23 struct Person 24 {25 int age; 26}; 27 28 struct Person p; 29 30 a = 10; 31} 32 33 int main () 34 {35 struct Date d1 = {2009, 8, 9}; 36 37 38 test2 (); 39 40 // The test2 function cannot be used to define the type 41 // struct Person p2; 42 43 return 0; 44} 45 46 // define the struct variable 47 void test () 48 {49 // 3rd methods for defining struct variables 50 struct {51 int age; 52 char * name; 53} stu; 54 55 struct {56 int age; 57 char * name; 58} stu2; 59 60 61/* struct type cannot be repeatedly defined 62 struct Student 63 {64 int age; 65 }; 66 67 struct Student 68 {69 double height; 70}; 71 72 struct Student stu; 73 */74 75/* incorrect syntax: repeated struct types 76 struct Student 77 {78 int age; 79 double height; 80 char * name; 81} stu; 82 83 struct Student 84 {85 int age; 86 double height; 87 char * name; 88} stu2; c 89 */90 91/* 92 this Code does two things 93 1. define struct type 94 2. use the newly defined type to define the struct variable 95 */96 // 2nd of the variables: define the type and define the variable 97/* 98 struct Student 99 {100 int age; 101 double height; 102 char * name; 103} stu; 104 105 struct Student stu2; 106 */107 108/* 109 // 1st ways to define variables: 110 // 1. type 111 struct Student112 {113 int age; 114 double height; 115 char * name; 116}; 117 118 // 2. variable 119 struct Student stu = {20, 1.78, "jack"}; 120 */121}