78 lines
3.1 KiB
HTML
78 lines
3.1 KiB
HTML
<HTML>
|
|
<HEAD><TITLE>QuickBASIC 3.0 - Long Entry</TITLE></HEAD>
|
|
<BODY>
|
|
|
|
<A HREF="ng1ded6.html">[<<Previous Entry]</A>
|
|
<A HREF="ng320.html">[^^Up^^]</A>
|
|
<A HREF="ng1eb89.html">[Next Entry>>]</A>
|
|
<A HREF="menu.html" >[Menu]</A>
|
|
<A HREF="info.html">[About The Guide]</A>
|
|
<HR>
|
|
<PRE>
|
|
<B>ON KEY Trap for Keypress</B>
|
|
|
|
<B>ON</B> <B>KEY</B>(<U>n</U>) <B>GOSUB</B> {<U>linenum</U> | <U>linelabel</U>}
|
|
|
|
Establishes a subroutine to which QuickBASIC will branch if it detects
|
|
a specified keypress. The trap must also be turned on by means of a
|
|
KEY(<U>n</U>) ON statement.
|
|
|
|
<U>n</U> A numeric expression in the range 1 to 20.
|
|
|
|
<U>linenum</U> The first line of a keypress-handling subroutine. Setting
|
|
<U>linenum</U> to 0 disables trapping.
|
|
|
|
<U>linelabel</U> A label identifying the first line of a keypress-handling
|
|
routine.
|
|
|
|
----------------------------------------------------------------------
|
|
|
|
<B>Notes:</B> {<U>linenum</U> | <U>linelabel</U>} must be defined at the main program
|
|
level.
|
|
|
|
The following keys may be trapped:
|
|
|
|
1-10 Function keys F1 through F10
|
|
11 Cursor Up
|
|
12 Cursor Left
|
|
13 Cursor Right
|
|
14 Cursor Down
|
|
15-20 Keys defined via KEY <U>n</U>,
|
|
CHR$(<U>KBflag</U>)+CHR$(<U>scancode</U>)
|
|
|
|
When the keypress is detected, QuickBASIC branches to the
|
|
specified subroutine and temporarily suspends trapping (by
|
|
means of an implicit KEY(<U>n</U>) STOP statement). Trapping
|
|
automatically resumes when a RETURN from the handling
|
|
subroutine is executed (unless the handler explicitly
|
|
performs a KEY(<U>n</U>) OFF or KEY(<U>n</U>) STOP).
|
|
|
|
The key that produced the trap may not be determined by
|
|
means of INPUT$ or INKEY$.
|
|
|
|
All event trapping is temporarily disabled when QuickBASIC
|
|
is executing an error-handling routine (established via an
|
|
ON ERROR statement).
|
|
|
|
ON KEY may be used to trap Ctrl-Break and Ctrl-Alt-Del,
|
|
thereby preventing a user from breaking out of a program.
|
|
|
|
If the "Checking Between Statements" option is in effect,
|
|
QB checks after each statement. If the "Event Trapping"
|
|
option is selected, QB checks after each new program line.
|
|
If neither option is selected, no trapping takes place.
|
|
|
|
For command-line compilation, /v enables checking after
|
|
each statement, and /w enables checking after each new
|
|
line. If neither switch is used, no trapping takes place.
|
|
</PRE>
|
|
<HR>
|
|
<B>See Also:</B>
|
|
<A HREF="ng16dd7.html">KEY(n)</A>
|
|
<HR>
|
|
This page created by ng2html v1.05, the Norton guide to HTML conversion utility.
|
|
Written by <A HREF="http://www.acemake.com/hagbard">Dave Pearson</A>
|
|
<HR>
|
|
</BODY>
|
|
</HTML>
|