Question

what is the difference between ''primitive''and ''defined data type''

Answer 1

HEY .
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Java has eight primitive type: int, double, float, long, short, byte, char, boolean. It means programmer can notdefine new primitive type. ... Referencetypes aggregate types that hold zero or more primitive values or objects.Primitive types require between one and eight bytes of memory.

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Answer 2

Primitive data types include integer , character , void , float etc..which are defined already inside the language i.e , user can use these data types without defining them inside the language. 
User defined data types are the data types which user have to define while or before using them.
For example:- In C language , structure and union are used as user-defined data types.

A user-defined data type (UDT) is a data type that derived from an existing data type. You can use UDTs to extend the built-in types already available and create your own customized data types.