Structure and Union (Self Study).pdfStructure and Union (Self Study).pdf

Lectures on Busy Bee Workshop 1
This session Outline
Structure
Union
Difference between them
Structure & Union -C
Structure & Union -C

Data Types
In C programming language, divide the data into
different types. The various data types are
• Simple Data type (Fundamental)
 Integer, Real, Void, Char
• Structured Data type (Derived)
Array, Strings
• User Defined Data type (Programmer)
Enum, Structures, Unions
Structure and Union
Structure and Union

Structure Data Type
1. user defined data type
2. Groups logically related data items of different data
types into a single unit.
3. All the elements of a structure are stored at contiguous
memory locations.
4. A variable of structure type can store multiple data items of
different data types under the one name.
5. As the data of employee in company that is name,
Employee ID, salary, address, phone number is stored in
structure data type.
Structure
Structure

Structure
Structure
Defining of Structure
A structure has to defined, before it can used. The syntax of
defining a structure is
struct <struct_name>
{
<data_type> <variable_name>;
……..
};

Structure
Structure
Example of Structure
The structure of Employee is declared as
struct employee
{
int emp_id;
char name[20];
float salary;
char address[50];
int dept_no;
int age;
};

Memory Space Allocation
8000
8002
8022
8024
8074
8076
employee
emp_id
name[20]
salary
address[50]
dept_no
age
Structure
Structure

Declaring a Structure Variable
A structure has to declared, after the body of structure
has defined. The syntax of declaring a structure is
struct <struct_name> <variable_name>;
The example to declare the variable for defined
structure “employee”
struct employee e1;
Here e1 variable contains 6 members that are defined
in structure.
Structure
Structure

Initializing a Structure Members
The members of individual structure variable is initialize
one by one or in a single statement. The example to
initialize a structure variable is
1)struct employee e1 = {1, “Suresh”,12000, “3 vikas
colony Madurai”,10, 35};
2)e1.emp_id=1; e1.dept_no=10;
e1.name=“Suresh”; e1.age=35;
e1.salary=12000;
e1.address=“3 vikas colony Madurai”;
Structure
Structure

Accessing a Structure Members
1. The structure members cannot be directly accessed in the
expression.
2. They are accessed by using the name of structure variable
followed by a dot and then the name of member
variable.
3. The method used to access the structure variables are
e1.emp_id, e1.name, e1.salary, e1.address, e1.dept_no,
e1.age.
4. The data with in the structure is stored and printed by this
method using scanf and printf statement in c program.
Structure
Structure

Structure Assignment
The value of one structure variable is assigned to
another variable of same type using assignment
statement. If the e1 and e2 are structure variables of
type employee then the statement
e1 = e2;
assign value of structure variable e2 to e1. The
value of each member of e2 is assigned to
corresponding members of e1.
Structure
Structure

Program to implement the Structure
Structure
Structure

Structure
Structure
Array of Structure
1. C allows to create an array of variables of
structure.
2. The array of structure is used to store the large
number of similar records.
3. For example to store the record of 100 employees
then array of structure is used.
4. This is similar to array.
5. The syntax to define the array of structure is
struct <struct_name> <var_name(array_name)>
[<value>];
For Example:-
struct employee e1[100];

Program to implement the Array of Structure
Structure
Structure

Structure
Structure
Structures within Structures
1. C define a variable of structure type as a member of other
structure type.
2. The syntax to define the structure within structure is
struct <struct_name>{
struct <struct_name>
{ <data_type> <variable_name>;
……..}<struct_variable>;
};

Structure
Structure
Example of Structure within Structure
The structure of Employee is declared as
struct employee
{
int emp_id;
char name[20];
float salary;
int dept_no;
struct date
{
int day;
int month;
int year;
}doj;
}e1;

Accessing Structures within Structures
For Example:-
e1.doj.day;
e1.doj.month;
e1.doj.year;
Pointers and Structures
The pointer variable to structure variable is declared as
struct employee *emp;
Access the Pointer in Structures
Access using arrow operator(->) instead of period operator(.).
For Example:
emp->name; emp->emp_id;
Structure
Structure

Passing Structure to Function
For Example:
printdata (struct employee e1); // Function calling
void printdata( struct employee emp) // Function defnition
{
…….
}
Function Returning Structure
struct employee getdata( )
{
….
return e1;
}
Structure
Structure

Union
Union
Union Data Type
1. A union is a user defined data type like structure.
2. The union groups logically related variables into a single
unit.
3. The union data type allocate the space equal to space
need to hold the largest data member of union.
4. The union allows different types of variable to share same
space in memory.
5. There is no other difference between structure and union
than internal difference.
6. The method to declare, use and access the union is same
as structure except the keyword union.

Union
Union
Example of Union
The union of Employee is declared as
union employee
{
int emp_id;
char name[20];
float salary;
char address[50];
int dept_no;
int age;
}e;

Memory Space Allocation
8000
emp_id, dept_no, age
8002
salary
8004
name
8020
address
8050

Union
Union
Example Program of Union

Structure and Union (Self Study).pdfStructure and Union (Self Study).pdf

Structure and Union (Self Study).pdfStructure and Union (Self Study).pdf

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