The Programmer's Guide to TRSDOS Version 6 - Tim Mann's Home ...

Exit:
A Will contain an error return code if an error was encountered.
Z set if the operation was successful.
7.6.91 @WEOF SVC-74
This SVC will force the system to update the directory entry with the current end-of-file
information. The file's FCB will remain in an open state.
Registers Affected: AF.
Entry:
DE A pointer to the FCB for the file to WEOF.
Exit:
A Will contain an error return code if an error was encountered.
Z Set if the operation was successful.
7.6.92 @WHERE SVC-07
This SVC can be invoked to determine the address of the calling routine. It can be useful
for small routines that are to be made run-time relocatable.
Registers Affected: AF, HL.
Exit:
HL Returns the memory address following the SVC instruction.
7.6.93 @WRITE SVC-75
This SVC will cause a write to the next record identified in the FCB. If the file's
Logical Record Length (LRL) identified in the FCB is less than 256, then the logical
record in the user buffer will be transferred to the file. If LRL is equal to 256, a full
sector I/O will be made using the disk I/O buffer identified at file open time.
Registers Affected: AF.
Entry:
DE A pointer to the FCB for the file to write.
HL A pointer to the user record buffer (UREC) containing the logical record
(where the LRL is 256).
Exit:
A Will contain an error return code if an error was encountered.
Z Set if the operation was successful.
7.6.94 @WRSEC SVC-53
This SVC will pass a function code 13 to a disk driver. It is used to write a physical
sector of data to the disk. See chapter 4 for additional information.
Registers Affected: AF [Note: DOS saves BC, IY; drivers should save any other
registers they use].
Entry:
C Contains the logical drive number.
D Contains the number of the cylinder to write.
E Contains the number of the sector to write.
HL A pointer to the buffer containing the sector of data.
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