Q57890: Overhead for /V and /W Event Trapping Is Reduced in BASIC 7.00

Article: Q57890
Product(s): See article
Version(s): 6.00 6.00b 7.00 | 6.00 6.00b 7.00
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | | mspl13_basic
Last Modified: 31-JAN-1990

The code overhead for BC /V is only 3 bytes per statement, and the
code overhead for BC /W is only 3 bytes per labeled or numbered line,
in Microsoft BASIC Professional Development System (PDS) Version 7.00
for MS-DOS and MS OS/2.

The overhead for these event trapping options is 5 bytes in Microsoft
QuickBASIC Versions 4.00, 4.00b, and 4.50 for MS-DOS, and in Microsoft
BASIC Compiler Versions 6.00 and 6.00b for MS-DOS and MS OS/2.

Event trapping for the ON <event> GOSUB statements is handled by
polling. The <event> can be COM(n), KEY(n), PEN, PLAY(), STRIG, and
TIMER. In BASIC 6.00, 6.00b, and 7.00, you can also use ON SIGNAL and
ON UEVENT.

At various points in your code, as controlled by the /V and /W options
and the <event> ON and <event> OFF statements, the compiler places a
call instruction to a routine that checks for events. /V places the
call on every statement in the module. /W only places the call on
every numbered or labeled line in the module. In QuickBASIC Versions
4.00, 4.00b, and 4.50 and in Microsoft BASIC Compiler 6.00 and 6.00b,
this call occupies 5 bytes. In BASIC 7.00, this has been reduced to 3
bytes per call.

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