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Introduction of Structure in DataStructure, C Programming

       The standard data types available in any programming language like “C” cannot meet every need of the user his for data handling. It is not possible to implement s all real life activities and entities by using only standard data types. So the help of available standard data type by clubbing them into a single unit. Structures are user defined data types, which are used to club dissimilar data member into a single unit. That unit is the new user defined data type and can be used to declare the data variables according to the requirement.
             Usually the structures are defined to club the similar, related characteristics of an object derived as new data type.

Defining a structure  

            A structure is defined using a keyword struct and giving a name to the structure data type and declaring each individual members (elements) as normal declaration in a block (i.e., within a pair of curly brackets, {}) and ending the block by semicolon; because of data definition. The syntax of structure definition is as follows:
        struct datatype_name
        {
        Member1 declaration;
        …
       Membern declaration;
        };
Here “struct” is a key word. Datatype_name can be any valid identifier, used as a name for new data type. For example, an employee structure may be defined as:
        Struct emp
           {
             Int eno;
             Char ename [21];
             Float salary;
           };
Here “struct emp” is a new user defined data type (note: not a variable) and can be used to declare the variables of that type, like struct emp e1, e2, earr[10] etc. The variables defied inside the struct like eno, ename  and salary are the members of struct emp and are also called as elements of the structure. With the help of a variable of the type struct emp, the individual members (elements) may be referred by means of dot (.) operator also called as member access operator. At the time of defining data type the variables may be declared after closing curly bracket ‘}’, before the semi colon ‘;’ as shown below:
struct emp
{
 Int eno;
 char ename [21];
 float salary;
} e1,e2;
The structure variables can be initialized at the time of declaration as follows:
struct emp
{
  Int eno;
  Char ename [21];
  Float salary;
} e1={101,”Sachin”, 12360.55};


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             In memory the linked list is stored in scattered cells (locations).The memory for each node is allocated dynamically means as and when required. So the Linked List can increase as per the user wish and the size is not fixed, it can vary.

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