Discuss DOS function call with one example.

DOS function call:

So as to use DOS function calls, always place the function number in register AH and load all other pertinent information in registers, as described in the entry data table. Once it is accomplished, follow along with an INT 21H to execute the DOS function.

Illustration:      MOV AH, 6

                        MOV DL, 'A'

                        INT 21H.

Illustration shows how to display an ASCII A on the CRT screen at the current cursor position along with a DOS function call.