Q66691: No "Block IF Without END IF" Using IF…THEN REM in QB/QBX.EXE

Article: Q66691
Product(s): See article
Version(s): 6.00 6.00b 7.00 7.10 | 7.00 7.10
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | B_QUICKBAS buglist6.00 buglist6.00b buglist7.00 buglist7.10 | mspl13_basic
Last Modified: 14-NOV-1990

In compiled BASICs that support block IF statements, the following
statement correctly implies a block IF ... END IF statement, instead
of a single-line IF statement syntax (whereas GW-BASIC correctly
treats this as a single-line IF because GW-BASIC has no block IF
syntax):

   IF expression THEN ' Comment

However, using a THEN REM statement, as follows, poses a problem:

   IF expression THEN REM Comment

The problem is that the QBX.EXE (or QB.EXE) environment interprets
THEN REM as indicating a single-line IF statement, whereas BC.EXE
compiler interprets THEN REM as indicating a block IF.

This inconsistency applies to Microsoft QuickBASIC versions 4.00,
4.00b, 4.50 (buglist4.00, buglist4.00b, buglist4.50) for MS-DOS; to
Microsoft BASIC Compiler versions 6.00 and 6.00b for MS-DOS and MS
OS/2; and to Microsoft BASIC Professional Development System (PDS)
versions 7.00 and 7.10 for MS-DOS and MS OS/2.

When compiling the code example below, BC.EXE gives a "Block IF
without END IF" error but the QBX.EXE or QB.EXE environment doesn't
give an error, and interprets the IF ... THEN REM statement as a
single-line IF statement. If an END IF statement is put at the end of
the code, the code example will compile with no error in BC.EXE but
the QBX.EXE or QB.EXE environment will give an "END IF without block
IF" error.

The problem is caused by the REM statement on the IF line. In the
QBX.EXE or QB.EXE environment, this case is interpreted as a
single-line (non-block) IF. The BC.EXE compiler, however, strips off
the REMark and interprets the line as the start of a block IF
statement.

Microsoft is researching which consistent syntax requirement should be
adopted for IF ... THEN REM and will post new information here as it
becomes available.

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

IF a = 3 THEN REM  Gives "Block IF without END IF" in BC.EXE
a = 5

To a avoid this problem, a remark should never be placed after a THEN
statement. For example, the following code example avoids this problem
by putting the remark on a separate line:

REM   This remark doesn't cause a problem.
IF a = 3 THEN
a = 5
END IF

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