In Matlab, How to use a function within a function without creating another fun_name.m file?

The following info might be obvious to you!

Well, you know usually in matlab, each function has to be declared into a separate fun_name.m file. In this case the objective is to allow other scripts to call this function.

But, if I need a function to be used inside a function which does not need to be called from the outside then how to do that?

It's damn obvious but I needed some time to figure it out :-)

function return_val=function_to_be_called (parameters of function_to_be_called )

% main code for function_to_be_called
% Here You may call internal_function

function val=internal_function (parameters of internal_function )
% your code
end % end of internal_function

end % end of function_to_be_called