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Q45451: CLEAR Resets ON ERROR GOTO and Turns Off Error Trapping

Article: Q45451
Product(s): See article
Version(s): 3.00 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | SR# S890224-103 B_BasicCom | mspl13_basic
Last Modified: 13-DEC-1989

The CLEAR statement in a QuickBASIC program turns off error handling
routines. Any error that happens after a CLEAR statement is not
trapped by an error handling routine that was initiated before the
CLEAR statement. To trap errors after a CLEAR statement, you must
reinstate the error handling routine with a new ON ERROR GOTO clause.

This applies to Microsoft QuickBASIC Versions 3.00, 4.00, 4.00b, and
4.50, and Microsoft BASIC Compiler Versions 6.00, 6.00b for MS-DOS and
MS OS/2, and Microsoft BASIC PDS 7.00 for MS-DOS and MS OS/2.

The following two programs show an error trapping routine that does
not work correctly and an error trapping routine that does work:

Program 1
---------

REM  This error handling routine will not trap the error.
  ON ERROR GOTO Handler
  CLEAR
REM The ERROR handling routine is now turned off
  ERROR 1
END
Handler: Print "In the ERROR Handler"
         RESUME

The output for this program is only an error message from QuickBASIC.

Program 2
---------

REM This ERROR Handling routine will trap the error.
  ON ERROR GOTO Handler
  CLEAR
REM The ERROR Handling routine is now turned off.
  ON ERROR GOTO Handler
REM The ERROR Handling routine is now turned back on.
  ERROR 1
END
Handler : Print "In the ERROR Handler"
          RESUME

The output for this program is as follows:

   In the ERROR Handler

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