Q31506: Fixed-Length String Illegal in FIELD; QB.EXE Wrongly Allows It

Article: Q31506
Product(s): See article
Version(s): 4.00 4.00b
Operating System(s): MS-DOS
Keyword(s): ENDUSER | buglist4.00 buglist4.00b fixlist4.50 | mspl13_basic
Last Modified: 7-SEP-1989

When you use a fixed-length string variable in a FIELD statement (to
define the buffer for a RANDOM access file), the BC.EXE compiler
correctly gives the error message "Variable-length string required."
However, the QB.EXE editor fails to warn you against using a
fixed-length string in FIELD statement, and the program runs and
ignores the fixed-length string variable in the FIELD statement.

Microsoft has confirmed this to be a problem in the QB.EXE editor in
QuickBASIC Versions 4.00 and 4.00b. This problem was corrected in
QuickBASIC Version 4.50 where the "Variable-length string required"
error message correctly displays in the QB.EXE editor as well as when
compiled with BC.EXE, when you attempt to use a fixed-length string
variable in a FIELD statement.

Please note that QuickBASIC Versions 3.00 and earlier don't have
fixed-length strings.

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

When you use the first DIM statement in the program below, QB.EXE
fails to give an error message on the FIELD statement, and "lastname"
is treated as a variable not connected with the FIELD statement and is
completely ignored in the FIELD statement. The same DIM correctly
gives a "variable length string required" error when compiled with
BC.EXE. The code example is as follows:

DIM lastname AS STRING * 6  ' Fixed-length string in FIELD is not OK.
'DIM lastname AS STRING     ' OK, since AS STRING is variable-length.
OPEN "Hunkfile" FOR RANDOM AS #1 LEN = 10
FIELD #1, 6 AS lastname, 4 AS firstname$
LSET lastname = "Cruise"
LSET firstname$ = "Tom"
PUT #1, 1
LSET lastname = "Gibson"
LSET firstname$ = "Mel"
PUT #1, 2
CLOSE #1
OPEN "hunkfile" FOR RANDOM AS #1 LEN = 10
FIELD #1, 6 AS lastname, 4 AS firstname$
GET #1, 1
PRINT firstname$; lastname
GET #1, 2
PRINT firstname$; lastname
CLOSE #1

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