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====== Int 21H, AH=25H ======

===== Version =====

1 and higher

===== Brief =====

SET INTERRUPT VECTOR

===== Family API =====


===== Input =====

        AH = 25h
        AL = interrupt number
        DS:DX -> new interrupt handler

===== Return =====

none

===== Notes =====

this function is preferred over direct modification of the interrupt vector table
          
some DOS extenders place an API on this function, as it is not directly meaningful in protected mode
          
under DR DOS 5.0-6.0, this function does not use any of the DOS-internal stacks and may thus be called at any time; however, under Novell DOS 7.0 - DR-DOS 7.02, this function was not reentrant. Since 1998/05/29, DR-DOS 7.03 no longer uses any internal stacks and tests for this function much earlier, to allow a minimal stack usage of just two words in addition to the IRET frame, allowing it to be called from INT 21h functions, specificially device drivers.  This fixes the MCS SMB client
          
Novell NetWare (except the new DOS Requester) monitors the offset of any INT 24 set, and if equal to the value at startup, substitutes its own handler to allow handling of network errors; this introduces the potential bug that any program whose INT 24 handler offset happens to be the same as COMMAND.COM's will not have its INT 24 handler installed
         
===== See also =====

 AH=[[en:docs:dos:api:int21:35|35h]]

===== Note =====

Text based on [[http://www.cs.cmu.edu/~ralf/files.html|Ralf Brown Interrupt List Release 61]]

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