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what is the differance between int 27h and 31h service of int 21h

b_ahmed_mdb_ahmed_md Member Posts: 17
hello all,

while programming TSRs, i had gone through 2 interrupt services for TSRs. one is int 21h, which is purely for TSRs then what about the int 21h service 31h. in one manual it had given that it is also for the TSRs? then what is the differance?.

Thanking u.

Comments

  • jeffleydajeffleyda Member Posts: 390
    : hello all,
    :
    : while programming TSRs, i had gone through 2 interrupt services for TSRs. one is int 21h, which is purely for TSRs then what about the int 21h service 31h. in one manual it had given that it is also for the TSRs? then what is the differance?.
    :
    : Thanking u.
    :
    From the online interrupt service list:
    http://www.delorie.com/djgpp/doc/rbinter/ix/


    INT 27 - DOS 1+ - TERMINATE AND STAY RESIDENT

    DX = number of bytes to keep resident (max FFF0h)
    CS = segment of PSP
    Return: never[red]
    Notes: this is an obsolete call[black]
    INT 22, INT 23, and INT 24 are restored from the PSP
    does not close any open files
    the minimum number of bytes which will remain resident is 110h for
    DOS 2.x and 60h for DOS 3.0+; there is no minimum for DOS 1.x, which
    implements this service in COMMAND.COM rather than the DOS kernel
    SeeAlso: INT 21/AH=31h


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