Introduction
è Array can be used to represent a group of data items that belongs to the same type. Such as int or float so need to represent a collection of data items of different types using a single name at that time array can not be used.
è C supports a constructed data type known as structure. A Structure is a collection of one or more variables grouped as a unit under a single name for easy processing.
è A structure is a convenient tool for handling a group of logically related data items.For example , it can be used to represent a set of attributes such as Employee_ name,Department,Salary etc.
Defining a Structure
è The structure consists of a number of data items grouped together but unlike array , each data item in the group need not be of the same type. It may consist data of different types
è The syntax for declaring the structure is as follows:
struct tag_name
{
Data_type member 1;
Data_type member 2;
};
è As shown in above syntax struct is a keyword.
è Tag_name is the name that identifies structure of this type.
è member1,member2 …are individual member declaration with their data type
è The struct template is terminated with a semicolon. The entire definition is considered as a statement.
Ex
struct employee
{
int no;
char name[15];
float salary;
};
Here, struct declares the structure to hold detail of three variables. These fields are called structure elements or member. Each member may belong to different type of data.
Declaring Structure variables:
è After defining a structure data type need to declare one or more variables to be of that type.
è A structure variable declaration is similar to the declaration of variable of any other data types.
è It includes the following elements.
· struct keyword
· the structure tag name
· List of variable name separated by commas.
· a terminating semicolon.
Ex
struct employee
{
int no;
char name[15];
float salary;
};
struct employee e1,e2,e3;
è With using this method structure variable can be declared any where in the program.The members of a structure themselves are not variables.They do not occupy any memory until they are associated with the structure variable such as e1.
è It is also allowed to combine both the structure definition and variables declaration in one statement.
Ex, struct employee
{
int no;
char name[15];
float salary;
}e1,e2,e3;
The use of tag name is optional.
Ex Struct
{
int no;
char name[15];
float salary;
}e1,e2,e3;
Here e1,e2,e3 are declared as a structure variable but doesn’t include a tag name for later use in declarations.
è The keyword typedef is also using to define a structure. such as
typedef struct
{
type member1;
type member2;
type member3;
}type_name;
Here, the type_name represents structure definition associated with it and therefore can be used to declare structure variable.
ex, type_name var1,var2,var3....;
Accessing Member of Structure
A member of a structure can be accessed and used individually in a problem.For thet consider following syntax:
struct_var_name.member_name
Here, the struct_var_name is the name of structure variable and member name is the name of variable which is member of structure.It can be accessed using the dot(.).
Ex
struct employee
{
int no;
char name[15];
float salary;
};
struct employee e1;
e1.no=5;
strcpy(e1.name,”xyz”);
e1.salary=1000;
The structure is mainly used to store a record that contain different data type.
Structure Initalization
A structure can be initialized by specified the values of data members just after the declaration of structure.
Ex
struct emp
{
int no;
char name[15];
floalt salary;
};
void main()
{ //initialization
struct emp e1={1,”xyz”,5000};
struct emp e2={2,”abc”,6000};
printf(“\n No Name Salary”);
printf(“\n%d %s %f”,e1.no,e1.name,e1.salary);
Printf(“\n%d %s %f”,e2.no,e2.name,e2.salary);
}
