Chapter 10 C Structures and Unions

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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.

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

$type: struct struct_type { type1 id1; type2 id2; }; E.g.$ $, struct student_info { char[20] name; int age; };$

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

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

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

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

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

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

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

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

Arrays of Structures (2/2) The array of structures can be simply manipulated as arrays

25 Struct Array Example (1/2)

26 Struct Array Example (2/2)

Loops / Repetition Statements. There are three loop constructs in C. Example 2: Grade of several students. Example 1: Fixing Bad Keyboard Input

Loops / Repetition Statements. There are three loop constructs in C. Example 2: Grade of several students. Example 1: Fixing Bad Keyboard Input Loops / Repetition Statements Repetition s allow us to execute a multiple times Often they are referred to as loops C has three kinds of repetition s: the while loop the for loop the do loop The programmer