Int 21 Fn 01  - DOS 1+ - Read Character From Standard Input, With Echo     [D]

   AH = 01h

Return: AL = character read

Notes:  Break are checked, and INT 23 executed if read
   character is echoed to standard output
   standard input is always the keyboard and standard output the screen
     under DOS 1.x, but they may be redirected under DOS 2+

See Also: AH=06h,AH=07h,AH=08h,AH=0Ah