Q41389: SIGNAL Is BASIC Reserved Word; SIGNAL ON Usable Only in OS/2

Article: Q41389
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom SR# S890125-25 | mspl13_basic
Last Modified: 15-DEC-1989

The ON SIGNAL(n) GOSUB and SIGNAL ON statements are implemented only
in OS/2 protected mode for programs compiled with BC.EXE in Microsoft
BASIC Compiler Versions 6.00 and 6.00b or Microsoft BASIC PDS Version
7.00.

SIGNAL is a reserved word in QuickBASIC Versions 4.00, 4.00b, and
4.50, Microsoft BASIC Compiler Versions 6.00 and 6.00b, and Microsoft
BASIC PDS Version 7.00. However, the SIGNAL statements will be
accepted only by BASIC compiler 6.00 and 6.00b and BASIC PDS 7.00 when
compiling in protected mode under OS/2. In all other situations, a
SIGNAL statement results in an "Advanced feature unavailable" error
message.

The BC.EXE compiler that comes with BASIC compiler 6.00 and 6.00b and
BASIC PDS 7.00 supports the ON SIGNAL(n) GOSUB and SIGNAL ON
statements, as documented in Section 5 (Pages 27-29) of "Microsoft
BASIC Compiler 6.0: User's Guide" for Versions 6.00 and 6.00b for MS
OS/2 and MS-DOS and the "Microsoft BASIC 7.0: Language Reference"
manual on Pages 341-342.

Below is an example of the correct use of the ON SIGNAL(n) GOSUB and
SIGNAL ON statements. This program is supported only if you compile in
OS/2 protected mode with BC.EXE from Microsoft BASIC Compiler Version
6.00 or 6.00b, or Microsoft BASIC PDS Version 7.00, and run the
resulting executable in protected mode:

   PRINT "This program traps CTRL+BREAK in OS/2. Try it."
   ON SIGNAL(4) GOSUB trap
   SIGNAL(4) ON
   10 a$ = INKEY$
   IF a$ = "" THEN GOTO 10
   END
   trap:
     PRINT "CTRL+BREAK trapped. Press any key to quit"
     RETURN

The above program always reports "Advanced feature unavailable" when
run in real mode (DOS) as a compiled executable or when run inside the
QuickBASIC QB.EXE or the BASIC PDS 7.00 QBX.EXE environments.

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