it show the valid and invalid classes

Equivalence Class is a collection of test inputs such that 
one input check validates all input values in that class.

the values maximum and minimum that to be checked for the
application.

ECP is BB testing technique that divide input domain of a
program into classes.Like

1.If I/P condition specifies range, one valid and two
invalid classes are defined
2.If I/P condition requires specific value,one valid and two
invalid classes are defined
3.If I/P condition is member of set,One valid and one
invalid classes are defined
4.If I/P condition is Boolean,One valid and one Invalid
classes are defined.

An equivalence class is a subset of data that is 
representative of a larger class. Equivalence partitioning 
is a technique for testing equivalence classes rather than 
undertaking exhaustive testing of each value of the larger 
class. For example, a program which edits credit limits 
within a given range (1,000 - 1,500) would have three 
equivalence classes:

< 1,000 (invalid)
Between 1,000 and 1,500 (valid)
> 1,500 (invalid)

>> Divide Test Data in to ..

Invalid, Valid, Invalid ... Classes.

Example: For getting licence you must be atleast 18 years of
age. And you can not get licence if your age is 80 years or
more. So if we divide this data using equi class
partitioning then it will be as following:

<15,40,90>