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Q39578: CHR$(0) PRINTs As Space to Screen; LPRINTs Nothing to Printer

Article: Q39578
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom SR# S881212-23 | mspl13_basic
Last Modified: 21-DEC-1988

CHR$(0) (a null byte) is a non-printable character in MS-DOS. However,
the PRINT and PRINT USING statements in BASIC print this character as
a space.

Sending CHR$(0) to the following MS-DOS logical device names will
print nothing:

  "CONS:"
  "LPTn:"
  "COMn:"
  "SCRN:"

Likewise, printing CHR$(0) with the LPRINT or LPRINT USING statements
sends nothing.

Fixed-length strings are initialized to null bytes. Printing these
fixed-length strings to the screen and to the printer will give
different column alignment. This difference can be circumvented by
using the STRING$() function to initialize the fixed length string
with spaces.

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

The following is a code example:

'The following piece of code will print an uninitialized fixed-length
'string to the screen and printer using the PRINT and LPRINT
'statements. Unless the STRING$() function is used to fill the
'fixed-length string with spaces, the hard copy and screen will show
'different column alignment.
TYPE aType
  Field1 AS STRING * 32    ' a fixed length string
END TYPE
DIM aVariable AS aType
CLS
' Comment out the following line to cause different column alignment
' between LPRINT and PRINT; otherwise columns will line up the same:
aVariable.Field1 = STRING$(32, " ")

' Use LPRINT:
FOR i = 1 TO 10: LPRINT : NEXT i
LPRINT "printing aVariable.Field1 to printer with 'xxxx' following"
LPRINT "1234567890123456789012345678901234567890"
LPRINT aVariable.Field1; "xxxx"
LPRINT "printing aVariable.Field1 with LPRINT USING '\     \xxxx'"
LPRINT USING "\     \xxxx"; aVariable.Field1
FOR i = 1 TO 10: LPRINT : NEXT i

' Use PRINT:
PRINT "printing aVariable.Field1 to screen with 'xxxx' following"
PRINT "1234567890123456789012345678901234567890"
PRINT aVariable.Field1; "xxxx"
PRINT "printing aVariable.Field1 with PRINT USING '\     \xxxx'"
PRINT USING "\     \xxxx"; aVariable.Field1

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