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

7.6.27 @DSPLY SVC-10
This SVC will display a message line to the *DO device. The line must be terminated with
either an (X'0D') or an ETX (X'03'). If an ETX terminates the line, the cursor
will be positioned immediately after the last character displayed.
Registers Affected: AF, DE.
Entry:
HL points to the 1st byte of your message.
7.6.28 @ERROR SVC-26
This SVC will provide an entry to post an error message. @ERROR will normally terminate
to the @ABORT SVC. If bit 7 of the error register is SET, the error message will be
displayed and return will be made to the calling program. If bit 6 of the error register
is reset, the complete error information shown below is displayed. If bit 6 is set, then
only the "Error message string" [see Chapter 8, the Appendix, Error Message Dictionary]
is displayed.
Registers Affected: AF [Note: not applicable if @ABORT option].
Entry:
C Error number with bits 6 and 7 optionally set.
DE Optional string buffer pointer used with CFLAG option.
It is possible to have @ERROR return the message string associated with the error
by setting bit-7 of the CFLAG$ (see SVC-101). This can be useful if you want to
control the positioning of the message. Also, in the case of compilers and
interpreters, it can be useful to use this option as a means of providing greater
flexibility to the application program.
*** Error code = xx, Returns to X'dddd'
Last SVC = nnn, Returned to X'rrrr'
7.6.29 @EXIT SVC-22
This is the normal SVC to perform a program exit and return to DOS. Alternatively, if
your program maintains the integrity of the stack pointer, then a simple RET instruction
will return to the system.
Registers Affected: Not applicable.
Entry:
HL Must be loaded with the return code (0 = no error).
7.6.30 @FEXT SVC-79
This SVC will set up a default file extension in the FCB if the file specification
entered contains no extension.
Registers Affected: AF.
Entry:
DE A pointer to the File Control Block.
HL Pointer to the 3-character default extension which must be stored in upper
case.
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