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Structure

A Structure is a Group of data items of

different data types held together in a single

unit.

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Declaring a Structure

struct sname

{

type var1;

type var2;

type var3;

.

.

type varN;

};

struct is a keyword to define a structure.

sname is the name given to the structure data type.

type is a built-in data type.

var1,var2,var3,..,varNare elements of structure

being defined.

Structure template

sname is called tag makes it possible to declare other

variable of the same structure type without having to

rewrite the template itself. Its a type name.tag is

optional.

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Eg to store information of an employee, our structure

declaration may look like as shown overleaf

struct employee_type

{

int code;

char name[20];

int dept_code;

float salary;

};

No variable has been associated with this structure

No memory is set aside for this structure.

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Declaring Variables of the Structure Type

Declares a variable employee of type employee_type

At this point, the memory is set asidefor the structure variable

employee.

We can also declare variable(s) of structure type alongwith the structure declaration.

struct employee_type employee;

struct employee_type

{

int code;

char name[20];

int dept_code;

float salary;

}employee

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Consider the declarations to understand how the elements

of the structure variables are stored in memory

struct example_type

{

char var1;

int var2;

float var3;

double var4;

};

struct example_type sample1;

Note: all members are stored in contiguous memory location in order in which they aredeclared.

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How the elements of the structure variables are

stored in memory

11971198

1199

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1201

1202

1203

1204

1205

1206

1207

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var 1

var 2

var 4

var 3

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Intializing Structures

struct student_type

{

int rollno;char name[25];

int age;

float height;};

struct student_type student=1000,Surbhi salaria,18,5.6-;

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Accessing Structure Elements

Elements are accessed using dot operator.

It provides a powerful and clear way to refer to an

individual element.

Syntax: sname.vname

sname is structure variable name.

vname is name of the element of the structure.Eg: the element of the structure variable student

can be accessed as

student.rollno,student.name,student.age,student.height

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WAP to display size of structure elements.Use sizeof() of operator.

main()

{struct book1

{

char book[30];

int pages;float price;

};

struct book1 bk1;

clrscr();

printf(\nSize of Structure elements\n);

printf(\nBook: %d,sizeof(bk1.book));

printf(\nPages: %d,sizeof(bk1.pages));

printf(\nBook:%d,sizeof(bk1.price));

printf(\nBook:%d,sizeof(bk1));

Output

Book : 30Pages:2

Price:4

Total Bytes:36

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Entering Data into Structuresstruct employee_type

{

int code;

char name[25];

char dept[15];

float salary;

};

main()

{

struct employee_type employee;

printf(\nEnter employee code:\n);

scanf(%d,&code);

printf(\nEnter name:\n);

gets(employee.name);

printf(\nEnter employees dept:\n);

gets(employee.dept);

printf(\nEnter employees salary:\n);

scanf(%f,&employee.salary);

continue

printf(\n\nParticulars of emp as entered by user\n);

printf(\nEmployees code:%d,employee.code);

printf(\nEmployees name:%s, employee.name);

printf(\nEmployees dept:%s,employee.dept);

Printf(\nEmployees sal:%f,employee.salary);

continue

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Use of Assignment Statement for Structures

Value of one structure variable can be assigned toanother variable of the same type using simple

assignment statement.if student1 and student2

are structure variable of type student_type,thenstudent2=student1;

Assigns value of structure variable student1 to

student2

Simple assignment cannot be used this way for

arrays.

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WAP to copy structure elements from one object to another object

void main()

{

struct disk

{

char co[15];

float type;

int price;};

struct disk d1=SONY,1.44,20-;

struct disk d2,d3;

strcpy(d2.co,d1.co); individual elements of d1 object are copied using

d2.type=d1.type; assignment statement

d2.price=d1.price;

d3=d2; // all the contents are copied to d3

clrscr();

continue

continue

printf(\n %s %g %d,d1.co,d1.type,d1.price);

printf(\n %s %g %d,d2.co,d2.type,d2.price);

printf(\n %s % %d,d3.co,d3.type,d3.price);

}

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Pointers and Structures

struct student_type student,*ptrIt declares a structures variable studentand a pointer variable ptrtostructure of type student_type.

ptr can be initialized with the following assignment statement

ptr=&student;HOW WE CAN ACCESS THE ELEMENTS OF STRUCTURE?

But this approach will not workbecause dot has higher priority

Correctly way to write is:

or

*ptr.rollno,*ptr.name,*ptr.age,*ptr.height

(*ptr).rollno,(*ptr).name,(*ptr).age,(*ptr).height

ptr->rollno,ptr->name,ptr->age,ptr->height

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Structure within Structure

We can take object of one structure as member in another structure.

Structure within structure can be used to create complex data applications.

Syntax: struct time

{

int second;

int time;

int hour;

}

struct t

{

int carno;

struct time st;

struct time et;

};

struct t player;

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main()

{

struct time

{

int second;

int minute;

int hour;

}

struct t

{

int carno;

struct time st;

struct time rt;

};

struct tr1;

clrscr();

scanf(%d,&r1.carno);scanf(%d %d %d,&r1.st.hour,&r1.st.minute,&r1.st.second);

scanf(%d %d %d,&r1.rt.hour,&r1.rt.minute,&r1.rt.second);

printf(\n \tCArno \n\tStarting time \n\t Reaching time\n);

printf(\t%d\t,r1.carno);

printf(\t%d:%d:%d\t\t,r1.st.hour,ri.st.minute,r1.st.second);printf(\t%d:%d:%d\t\t,r1.rt.hour,ri.rt.minute,r1.rt.second);

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Array of Structures

If we wish to process a list of values of structuretype,then we need an array of such structures.

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Declaring an Array of Structures

struct employee_type

{

int code;

char name[25];char dept[15];

float salary;

};struct employee_type employee[50];

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Accessing elements an array of structures

Individual elements of a structure in an array ofstructure are accessed by referring to

structure variable name.

1. Followed by subscript.

2. Followed by dot operator.

3. Ending with structure element desired.

Suppose we want to access salary of 7th

employee,we can do so by writing

employee[6].salary

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WAP to create an array of structure objects

main()

{

int k;struct time

{

int second;

int minute;

int hour;};

struct tt

{

int carno;

struct time st;

struct time rt;

};

struct tt r1[3];

clrscr();

printf(\n Carno Starting time Reaching time);

for(k=0;k

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Structure and Function

The relationship of structure with the function

can be viewed from three angles:-1. Passing Structures to a function.

2. Function Returning Structure.3. Passing array of Structures to Function.

Note:When a structure element is to be passed to any other

function,it is essential to declare the structure outside the

main() functioni.e global

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Read and display student grade by

using structure with functionstruct student

{

int rn;

char name[20];

char grade;}s;

main()

{

printf(\nEnter rollno,name and grade of student:\n);

scanf(%d %s %c,&s.rn,s.name,&s.grade);

display(s);

getche();

}

display(m)struct student m;

{

printf(\nRollno is %d,m.rn);

printf(\n Name is %s,m.name);

printf(\n Grade is: %c,m.grade);

grade;

}

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Passing of structure variables by value to a function

struct date

{int day;

int month;

int year;

};

void print_date(struct date);

void main()

{

struct date d={10,12,1997};

print_date(d);

}

void print_date(struct date a)

{rintf nDate in format %d %d %d a.da a.month a. ear

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Passing to the function by address

struct book{

char name[35];

char author[35];

int pages;

}b1;

void main()

{

---------

---------

show(&b1);

}

show(struct book *b2)

{

-------------------------------------

}

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Prog to pass address of structure variable to user defined function and

display the contents

struct book

{char name[35];

char author[35];

char author[35];

int pages;

}void main()

{

struct book b1=JAVA COMPETE REFERENCE,P.NAUGHTON,886-;

show(&b1);

}show(struct book *b2) pointer to structure

{

clrscr();

printf(%s %s %d,b2->name,b2->author,b2->pages);

}

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Passing of structure variables by reference to a function

struct date

{

int day;

int month;

int year;

};

main(){

struct date d;

void get_date(struct date *);

printf(Enter date in the format:\n);

get_date(&d);

printf(\nDate entered by you %d %d %d,d.day,d.month,d.year);

}

void get_date(struct date *a)

{ scanf(%d %d %d,&a->day,&a->month,a->year);

l f () d h

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Wap to pass structure elements to function print() and print the

elements

void main()

{struct boy

{

char name[25];

int age;

int wt;

};

struct boy b1=Amit,20,25-;

print(b1.name,b1.age,b1.wt);

}print(char *s,int t, int n)

{

printf(\n%s %d %d,s,t,n);

return 0;

}

Note:

We have passed base address of nameBut values ofage and wt.

Here values are passed using call by reference and call by

value

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Function Returning Structure

struct date

{

int day;

int month;

int year;};

main()

{

struct date d;

struct date get_date(void);

printf(\nEnter date in format day/month/year);

d=get_date();

printf(\nDAte entered by you is %d %d %d\n,d.day,d.month,d.year);

}

struct date get_date(void)

{

struct date a;

scanf(%d %d %d,&a.day,&a.month,&a.year);

return a;

}

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Union

Union:

Union is similar as structure. The major distinction between them interms of storage.

In structure each member has its own storage location whereas all

the members ofunion uses the same location.

The union may contain many members of different data type it can

handle only one member at a time union can be declared using the

keyword union.

Hold only one object at a time

Union requires bytes that are equal to the number of bytes requiredfor the largest members.

Eg: union contains char,int &long then the number of bytes reservedin the member for the union is 4 bytes.

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Union item

{

int m;

float x;char c;

} code;

This declare a variable code of type union item.

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outputmain()

{

union result

{

int marks;

char grade;

};struct res

{

char name[15];

int age;

union result perf;

}data;

printf(Size of union:%d,sizeof(data.perf));

printf(Size of structure:%d,sizeof(data));

}

Output:

Size of union: 2

Size of structure: 19