Transcript STRUCTURES AND UNIONS

STRUCTURES
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 
height && width && length
complex number ( 3+5i )
rectangular prism
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
Defining Structures 1
“complex_number”
is the tag name
“struct complex_number”
is the new type
struct complex_number
{
int real_part;
int imaginary_part;
};
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];
};
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;
s1
real_part
imaginary_part
s2
struct complex_number s2;
real_part
imaginary_part
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
height
width
length
Structures : Creating static arrays of objects
struct student_record
{ int ID;
char name[100];
};
// Creates an array of student records  “group”
group
struct student_record group[4];
group[0] 
ID
name
group[1] 
ID
name
group[2] 
ID
name
group[3] 
ID
name
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 );
size of
objects in array
number of
objects in array
(array size)
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
obj.height=10;
obj.width=15;
obj.length=40;
height=10
width=15
length=40
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
obj == *p
p->width=15;
p->length=40;
height=10
width=15
length=40
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
group[0]  ID=200710
name= “doddy”
group[1] 
name =??
ID=200711
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;
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 */
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;
Initialization of Structure Objects
1.
struct names {
char name[10];
int length;
int weigth;} man[3]= {
“Tom”, 180, 65,
“George”, 170, 68,
“Bob”, 190, 100 };
2.
struct names woman[2]={{“Mary”, 170, 55}, {“Sue”, 160,67}};
3.
struct names your;
your. name=“Jane”;
your.length=160;
your.weigth=50;
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; }
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
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 );
}
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;
}
Senem Kumova Metin
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;
}