STRUCTURES

1. STRUCTURES

2. Structures in C • A structure is • a convenient way of grouping several pieces of related information together • a collection of variables under a single name Examples : real number &&imaginary number complexnumber ( 3+5i) height &&width && length rectangular prism

3. Structures in C • The variables in structures can be of different types, and each has a name which is used to select it from the structure Example : ID (integer) && Name (char array)  A Student record • A structure is a new named type that may involve several different typed variables

4. Defining Structures 1 “complex_number” is the tag name struct complex_number { int real_part; int imaginary_part; }; “struct complex_number” is the new type

5. Defining Structures 2 • /* DEFINITION OF RECTANGULAR PRISM */ • struct rectangular_prism • { int height; • int width; • int length; }; • // name of new type?? • /* DEFINITION OF STUDENT RECORD */ • struct student_record • { int ID; • char name[100]; };

6. real_part real_part imaginary_part imaginary_part Structures : Creating objects struct complex_number { int real_part; int imaginary_part; }; // Below the definition of structure you can create // objects from it  “s1” and “s2” struct complex_number s1; struct complex_number s2; s1 s2

7. width length height Structures : Creating objects struct rectangular_prism { int height; int width; int length; }; // Below the definition of structure you can create // objects from it  “obj” struct rectangular_prism obj; obj

8. ID name ID name ID name ID name group[0]  group[1]  group[2]  group[3]  Structures : Creating static arrays of objects • struct student_record • { int ID; • char name[100]; }; • // Creates an array of student records  “group” • struct student_record group[4]; group

9. size of objects in array number of objects in array (array size) Structures : Creating dynamic arrays of objects • struct rec • { int ID; • char name[100]; • }; • // Creating a dynamic array • // of student records  “group” • struct rec * group; // DECLARES POINTER • group = ( struct rec * ) malloc ( sizeof (struct rec) * 4 );

10. width=15 length=40 height=10 Structures : Accessing members of structures struct rectangular_prism { int height; int width; int length; }; // Create an object from the structure defined above  “obj” struct rectangular_prism obj; // Members of the objects can be accessed by putting a dot // following the object name obj.height=10; obj.width=15; obj.length=40; obj

11. width=15 length=40 height=10 Structures : Accessing members of structures struct rectangular_prism { int height; int width; int length; }; struct rectangular_prism obj; // Create a pointer to point object “obj” struct rectangular_prism *p = &obj; (*p).height=10 // or obj.height or p->height=10 p->width=15; p->length=40; obj == *p

12. Structures : Accessing members of structures • // Defines structure • struct student_record • { int ID;char name[100]; }; • // Creates an array of student records  “group” • struct student_record group[2]; • group[0].ID=200710; • strcpy(group[0].name, “doddy”); • group[1].ID=200711; • strcpy(group[1].name,group[0].name); group ID=200710 name= “doddy” group[0]  group[1]  ID=200711 name =??

13. Structures : DECLARATION ALTERNATIVES Declaration 1 : struct record { int ID; char * name; char grade; }; struct record s1; struct record s2; struct record s3; Declaration 2 : struct record { int ID; char * name; char grade; } s1, s2; struct record s3;

14. Structures : DECLARATION ALTERNATIVES Declaration 1 : struct record { int ID; char * name; char grade; }; struct record s1; struct record s2; Declaration 3 : struct { int ID; char * name; char grade; } s1, s2; /* no tag name */ /* no permission to declare other variables of this type */

15. Structures : DECLARATION ALTERNATIVES Declaration 4 : struct record { int ID; char * name; char grade; }; typedef struct record rec; rec s1; struct record s2; Declaration 5 :/* high degree of modularity and portability */ typedef struct { int ID; char * name; char grade; } rec; rec s1; rec s2;

16. Initialization of Structure Objects • struct names { char name[10]; int length; int weigth;} man[3]= { “Tom”, 180, 65, “George”, 170, 68, “Bob”, 190, 100 }; • struct names woman[2]={{“Mary”, 170, 55}, {“Sue”, 160,67}}; • struct names your; your. name=“Jane”; your.length=160; your.weigth=50;

17. Structures in Structures #include<stdio.h> struct physical_info { int length; int weigth; } ; struct record { int salary; int working_hour; struct physical_info man; } ; main() { struct record s1; s1.salary=10000; s1.working_hour= 6; s1.man.length=180; s1.man.weigth=78; }

18. Exercise 1 on Structures • Declare a structure for complex numbers (real and imaginary part) • Create 1 dynamic object (use pointers) • Ask user to fill the object • Print out the complex number as given below output Please give the values for complex number : 5 6 Complex number : 5 + 6i

19. Exercise 1 on Structures struct complex { int real; int imaginary; }; main() { struct complex * p; // Declare pointer for object // Memory allocation for object p=(struct complex *) malloc(sizeof(struct complex)); printf( " Please give the values for complex number : " ); scanf( "%d%d", &(p->real), & (p->imaginary) ); printf( "Complex number : %d + %d i", p->real, p->imaginary ); }

20. Exercise 2 : Define a function to add two complex numbers // A function to add two integers int add(int a, int b) { int result= a+b; return result; } • struct complex { int r; int i; }; • // A function to add two complex numbers • struct complex add ( struct complex a, struct complex b ) • { struct complex result; • result.r=a.r+b.r; • result.i=a.i+b.i; • return result; }

21. Exercise 3 on Structures struct rectangular_prism { int height; int width; int length; }; int volume(struct rectangular_prism x) {return x.height*x.width*x.length; } int area (struct rectangular_prism x) { return 2*x.width*x.lenght + 2*x.lenght*x.height + 2*x.width*x.lenght; }