what is the use of header file :<iostream.h> in c++

there is no use for iostream.h because it is obsolete. use iostream instead (without the .h extension) assuming your compiler supports it. Old compilers such as original Turbo C++ may recognaize iostream.h.

It defines the c++ iostream classes -- output text to the console monitor.

in which header file the operators will be stored in c++

what operators? please post code that is giving you problems and your compiler's error message(s). iostream operators are in iostream header file.

>in which header file the operators will be stored in c++
It could be a trick question... perhaps the question is asking about the normal C++ operators such as +,-, etc.. In that case, there is no header file as these are built into the C++ language.

what operators? please post code that is giving you problems and your compiler's error message(s). iostream operators are in iostream header file.

suppose ,if u do an addition in c++ , where the addition opertor will be stored in a program

you need iostream to get functions like cin and cout i think

suppose ,if u do an addition in c++ , where the addition opertor will be stored in a program

that's a pretty ambiguous question -- c++ has lots of addition operators and you can create your own. please post an example of what you mean.