1. Chapter 10 C Structures and Unions
C How to Program, 8/e, GE
© 2016 Pearson Education, Ltd. All rights reserved.

2. User-Defined Structure Types
A database is a collection of information subdivided into records.
A record is a collection of information of one data object (e.g., ID, name, and age of a student).
C allows us to define a new data type (called structure type) for each category of a structured data object.
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-2

3. Declaring Structure Types (1/3)
Syntax of the structure type: struct struct_type { type1 id1; type2 id2; … };
E.g., struct student_info { char[20] name; int age; };
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-3

4. Declaring Structure Types (2/3)
Syntax of the structure type: typedef struct{ type1 id1; type2 id2; … } struct_type;
E.g., typedef struct{ char[20] name; int age; } student_info;
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-4

5. Declaring Structure Types (3/3)
Declaration: student_info student1,student2;
Or (without typedef): struct student_info student1,student2;
A hierarchical structure is a structure containing components which are also structures. typedef struct{ int NumOfStudents; student_info students[20]; } class_info;
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-5

6. Struct example (without typedef)
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-6

7. Struct example (with typedef)
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-7

8. Manipulating Structure Types (1/2)
We can reference a component of a structure by the direct component selection operator, which is a period.
E.g., strcpy(student1.name, “Chao”); student1.age = 18; printf(“%s is in age %d\n”, student1.name, student1.age);
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-8

9. Component selection operator
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-9

10. Manipulating Structure Types (2/2)
The direct component selection operator has the highest priority in the operator precedence.
student1.age+student2.age+…;
The value of student1.age is referenced first.
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-10

11. Operator precedence in struct type
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-11

12. Manipulating Structure Types (2/2)
The copy of an entire structure can be easily done by the assignment operator.
student1 = student2;
Each component in one structure is copied into the corresponding component in the other structure.
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-12

13. Struct copy
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-13

14. Function with a Structured Input Parameter (1/2)
Suppose there is a structure defined as follows.
typedef struct{ char name[20]; double diameter; int moons; double orbit_time,rotation_time; } planet_t;
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-14

15. Function with a Structured Input Parameter (2/2)
When a structure variable is passed as an input argument to a function, all its component values are copied into the local structure variable.
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-15

16. Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-16

17. Function Returning a Structured Result Type (1/2)
The structure variable can also be used as the return value of a function.
Return time_of_day struct
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-17

18. timeupdate example
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-18

19. timeupdate example
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-19

20. Function Returning a Structured Result Type (2/2)
Suppose the current time is 21:58:32, and the elapsed time is 97 seconds.
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-20

21. Nested Structures (1/2)
Sample Struct Memory placement

22. Nested Structures (2/2)
Accessing Nested Struct members

23. Arrays of Structures (1/2)
We can also declare an array of structures.
E.g., typedef struct{ int id; double gpa; } student_t;
Usage: student_t stulist[50]; stulist[3].id = ; stulist[3].gpa = 3.0;
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-23

24. Arrays of Structures (2/2)
The array of structures can be simply manipulated as arrays of simple data types.
Copyright ©2004 Pearson Addison-Wesley. All rights reserved.
11-24

25. Struct Array Example (1/2)

26. Struct Array Example (2/2)