Int 21 Fn 5758  U - Headroom - API                                         [-]

   AX = 5758h
   BL = function
       00h ???
       01h get Headroom location

       Return: CF clear if installed
               AX = PSP segment of Headroom TSR
               BX = paragraphs of memory used by Headroom
           CF set if not (normal DOS return)

       Note:   this function is also used as an installation check
       02h get INT 21 handler

       Return: CF clear
           ES:BX -> Headroom's INT 21 handler

       Note: also sets unknown flag
       03h launch application???
       DS:SI -> 233-byte application record

       Return: ???
       04h ???
       ???

       Return: CF clear
       05h get swap directory

       Return: CF clear
           DX:AX -> ASCIZ swap directory name
       06h ???
       DX = ???

       Return: CF clear
       07h ???
       08h ???
       09h get current application

       Return: BX = application number
       0Ah ???
       DX = application number
       DS:SI = ???

       Return: ???
       0Bh ???
       0Ch ???
       DX = application number
       ???

       Return: ???
       0Dh ???
       DX = application number
       ???

       Return: ???
       0Eh get ???

       Return: CF clear
           AX = ???
       0Fh set ??? flag
       10h clear ??? flag
       11h find application by name
       DS:SI -> ASCIZ application name

       Return: CF clear
           AX = application number or FFFFh if not loaded
       12h ???
       DX = application number

       Return: CF clear
           ???
       13h ???

       Return: CF clear
       14h ???
       same as function 13h
       15h set ???
       DX = ???
       16h get ???

       Return: AX = ??? set by function 15h
       17h get ???

       Return: BX = ???
           CX = ??? (may be pointer in BX:CX)
       18h BUG: branches incorrectly due to fencepost error
Program: Headroom is a TSR/task switcher by Helix Software

See Also: AX=4C57h,AX=5757h