Actually int 21h function 2 will only display the single ascii character contained in dl. It will not output an entire string, and still less convert a floating point number into a string and then output it.

Beginners in assembly language always think that they are still programming in a high level language. Writing a procedure to convert a floating point number to a string, and then display it, is not a job I would particularly want, and I am not new to assembly language.