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Q50947: How to Get Extended Error in QuickBASIC Like EXTERR in GWBASIC

Article: Q50947
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | SR# S891107-92 B_BasicCom B_GWBasicI | mspl13_basic
Last Modified: 14-DEC-1989

The EXTERR function found in GW-BASIC Versions 3.20, 3.22, and 3.23 is
not built into QuickBASIC Versions 4.00, 4,00b, 4.50, or earlier, but
below is a code example calling a DOS interrupt that returns the same
information (concerning extended errors in MS-DOS 3.00 and later).

This code example applies to Microsoft QuickBASIC Versions 4.00,
4.00b, and 4.50 for MS-DOS, Microsoft BASIC Compiler Versions 6.00,
and 6.00b for MS-DOS, and to Microsoft BASIC PDS Version 7.00 for
MS-DOS.

The EXTERR function found in GW-BASIC takes a value of n as an
argument and returns a different set of values, depending on the value
of n. This return value gives detailed information on the most recent
DOS error. For all values of n, EXTERR returns 0 (zero) if there was
no previous DOS error, or if the version of DOS is earlier than 3.00.

   Value of n        EXTERR(n) Return Value
   ----------        ----------------------
   0                 Extended error code
   1                 Extended error class
   2                 Extended error suggested action
   3                 Extended error locus

To find what the error codes returned by EXTERR mean, look up the
values in "Advanced MS-DOS Programming, 2nd Edition" by Ray Duncan
(published by Microsoft Press, 1988) on Pages 145 and 146. This book
also documents the interrupt used below, along with the extended error
codes on Pages 453 through 456.

Compile and link with Microsoft QuickBASIC 4.00, 4.00b. and 4.50, or
with Microsoft BASIC Compiler 6.00 and 6.00b as follows:

   BC Test.bas;
   LINK Test.bas,,,BRUNxx.Lib+QB.Lib;

The "xx" in the library name is for the current version of the product
you are using (40, 41, 45, 60, or 61). For BASIC compiler 6.00 and
6.00b, use BRUNxxER.LIB (emulation math package) or BRUNxxAR.LIB
(alternate math package). For the alternate math library, you must
compile with the BC /FPa switch. If you compile with BC /O, link with
BCOMxx.LIB instead of BRUNxx.LIB.

Also, if you run this program in the QB.EXE environment, you must load
the Quick library QB.QLB as follows:

   QB /L QB.QLB

For BASIC PDS 7.00, compile and link as follows:

   BC Test.bas;
   LINK Test.bas,,,BRT70ENR.Lib+QBX.Lib;

The above example is for the math emulation, near strings, and real
mode run-time library. The other posible run-time libraries and their
corresponding compiler switches are as follows:

Library Name   Compiler Switches     Comments
------------   -----------------     --------

BRT70ENR.LIB                         Emulation math, near strings
BRT70ANR.LIB        /FPa             Alternate math, near strings
BRT70EFR.LIB        /Fs              Emulation math, far strings
BRT70AFR.LIB        /FPa /Fs         Alternate math, far strings

To use stand-alone libraries, use BCL70xxx.LIB instead of
BRT70xxx.LIB, and you must add the compiler switch BC /O.

For the QBX.EXE 7.00 environment, use QBX.QLB as follows:

   QBX /L QBX.QLB

Code Example
------------

REM $INCLUDE: 'QB.BI'
' For BC.EXE and QBX.EXE in BASIC 7.00, use the include file 'QBX.BI'

DIM Inregs AS RegTypeX, Outregs AS RegTypeX
CLS
INPUT "Enter the filename "; test$
test$ = test$ + CHR$(0)
Inregs.ax = &H3D00
Inregs.ds = VARSEG(test$)
' For BASIC Compiler 7.00 and QBX.EXE use SSEG(test$)
'     instead of VARSEG(test$)

Inregs.dx = SADD(test$)
CALL INTERRUPTX(&H21, inregs, outregs)
check = outregs.flags AND &H1
IF check = 1 THEN
   PRINT "The file was not found"
   Inregs.ax = &H5900
   Inregs.bx = inregs.bx AND &HFF
   CALL INTERRUPTX(&H21, Inregs, Outregs)
   PRINT "This is the error number"; Outregs.ax
ELSE
  PRINT "Your file was found, no extended error information is needed"
END IF
END

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