Q35245: Fixed-Length Strings Are Initialized to NULL (0), Not Blanks

Article: Q35245
Product(s): See article
Version(s): 4.00 4.00b
Operating System(s): MS-DOS
Keyword(s): ENDUSER | docerr B_BasicCom | mspl13_basic
Last Modified: 12-DEC-1989

The information below about fixed-length string arrays should be
inserted in the following manuals:

1. "Microsoft QuickBASIC 4.0: BASIC Language Reference"

2. "Microsoft BASIC Compiler 6.0: BASIC Language Reference" for
   Versions 6.00 and 6.00b for MS OS/2 and MS-DOS

On Pages 156, 174, and 352, under the DIM, ERASE, and REDIM
statements, the above manuals state that elements of string arrays are
initialized to null strings (strings of zero length). However, this is
not the case with fixed-length strings. Fixed-length strings are
initialized as a string of null bytes (with ASCII value of 0). The LEN
function always returns the complete length of the fixed-length
string. If a fixed-length string is initialized to "" (the null
string), it is completely filled with blank spaces (ASCII value of
32).

This documentation error was corrected in the QuickBASIC 4.50 and
Microsoft BASIC PDS 7.00 documentation.

The following is a code example:

DIM j AS STRING * 4
c$ = CHR$(0) + CHR$(0) + CHR$(0) + CHR$(0)
CLS
PRINT "j is printed between the stars:  *"; j; "*"
PRINT "j looks like a string of blanks, but it's not."
IF j = c$ THEN PRINT "j equals CHR$(0) + CHR$(0) + CHR$(0) + CHR$(0)."
IF j <> "" THEN PRINT "j does not equal "; CHR$(34); CHR$(34);
IF j <> "    " THEN PRINT " or "; CHR$(34); "    "; CHR$(34); "."
PRINT "But if I set j to "; CHR$(34); CHR$(34);
j = ""
IF j = "    " THEN
   PRINT " then j will equal "; CHR$(34); "    "; CHR$(34); "."
END IF

The following is the output from the program above:

j is printed between the stars:  *    *
j looks like a string of blanks, but it's not.
j equals CHR$(0) + CHR$(0) + CHR$(0) + CHR$(0).
j does not equal "" or "    ".
But if I set j to "" then j will equal "    ".

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