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The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

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include vmm.inc
include blockdev.inc
 
mov     ax, 1607h                   ; Device callout
mov     bx, BlockDev_Device_ID      ; Block device ID
mov     cx, BlockDev_API_Int13_Chain_Check
int     2Fh
 
jcxz    okay                        ; zero if okay to load block device
 
The BlockDev_API_Int13_Chain_Check function notifies TSRs and MS-DOS device
drivers that have hooked the ROM BIOS Interrupt 13h address that a block
device is about to load. This notification gives the TSR or device driver a
chance to cancel the loading.
 
Return Value
 
The TSR or device driver sets the CX register to zero if it is permissible
for block devices, such as WDCTRL, to load even though the MS-DOS Interrupt
13h chain has been modified.
 
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