Electric charge

it is found experimentally that the charges are of two types

1. Positive charge

2. Negative charge

Positively charged body means deficiency of electrons in the body and a negatively charged body means excess of electrons 

How much greater is one micro coulomb compared to an electronic charge?

10¹³  times

Structures 

It is a user defined data type which represents a collection of logically related data items.It can represent a group of different types of data under a common name.

Structure Definition 

 The  syntax to define  the structure is,

struct structure _tag

{

data_type variable 1;

data_type variable 2;

...................................

Data_type variable N;

};

Struct is the  keyword  to define a structure. Structure _tag(or structure _name) is an identifier and  variable 1,variable 2,.....variable N are  identifiers  to represent the  data  items  constituting  the grouped data.

The  members of  a structure is also  called  structure elements.

eg., struct  student

        {

        int age;

        Char name [10];

         float fee;

        };

Here student  is a structure name and age, name, fee are elements of structure 

Variable Declaration and Memory allocation 

A variable is required to refer to a group of  data. Once  we have defined a structure data type, variable is declared using the following syntax :

struct structure _tag  var1, var2, ......., varN;

                               OR

structure _tag var1, var2, ......., varN;

Here var1, var2,  ........, varN; are the structure variable.

eg., struct student personal, acdemic;

        Variable declaration statement causes memory allocation as per the size of the data type. The size  depends upon the definition of  the structure. A structure variable can be declared along  with the definition also.

eg., struct student

        {

         int age;

         char name [10];

          float fee;

          } personal, academic ;

Note: There is a limitation in this type of definition cum declaration. If we want to declare variables, to define functions, or to specify arguments using this structure later in the program, it is not possible since there is no tag to refer.

Variable Declaration and  Memory allocation 

A variable is required to refer to a group of data. Once we have defined a structure data type, variable is declared using the following syntax:

struct structure _tag  var1, var2, ........., varN;

                                OR

structure_tag  var1, var2, ......., varN;

Here var1, var2, ........, varN, are the structure variable.

eg., struct student personal, academic;

        Variable declaration statement causes memory allocation as per the size of the data type. The size depends upon the definition of the structure. A structure variable can be declared along  with the definition also.

eg., struct student

        {

         int age;

         char name  [10];

         float fee;

         } personal, academic ;

Note:There is a limitation in this type of definition cum declaration. If we want to declare variables, to define functions, or to specify arguments using  this  structure later  in  the program, it is not possible since there is no tag to refer.

Variable Initialisation 

During the  declaration of variables, they can be assigned with some values. This is known as initialisation. Its syntax is,

structure _tag  variable = {value1,  value2, ..........., valueN};

eg., student  s = {14, "Aryan", 500.00};

Accessing Elements of structure 

The elements  of a structure are accessed using the dot (.) Operator or period operator. The syntax for accessing elements is, structure_variable. element _name

eg.,  s.age;

         s.name;

Nested Structure 

An element of a structure may  itself itself be another  structure. Such a structure is known as nested structure. The concept of nesting enables the building of powerful data structures.

eg.,  struct dob

        {

         int  d,m, y;

        };

        struct student

        {

         char name [10];

         int  age ;

         dob date;

         };

Difference between array and structure 

Array

. It is a derived data type.

. A collection of same type  of data.

. Elements of an array are referenced using the corresponding subscript.

. When  an element of an array becomes another array, multi-dimensional array is formed.

. Array of structure is possible.

Structure

. It is a user-defined data type.

. A collection of different types of data.

. Elements of structure are reference using dot operator(.)

. When an element of an structure becomes another structure, nested structure is formed.

. Structure can contain arrays as elements.