DOCUMENT:Q73320 17-DEC-2000 [msdos]
TITLE :GW-BASIC/BASICA Keywords Not Supported in QBasic
PRODUCT :Microsoft Disk Operating System
PROD/VER:MS-DOS:5.x,6.0,6.2,6.21,6.22
OPER/SYS:
KEYWORDS:
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The information in this article applies to:
- Microsoft MS-DOS operating system versions 5.0, 5.0a, 6.0, 6.2, 6.21, 6.22
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SUMMARY
=======
The following GW-BASIC/BASICA keywords are not supported in QBasic:
AUTO EDIT MERGE RENUM
CONT LIST MOTOR SAVE
DEF USR LLIST NEW USR
DELETE LOAD
The following keywords behave differently in QBasic than in BASICA:
BSAVE BLOAD CALL ABSOLUTE
CHAIN COMMON DECLARE
DEFtype DIM DRAW
EOF FIELD PLAY
MORE INFORMATION
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The different behavior of the keywords in QBasic is as follows:
Keyword Description
------- -----------
BSAVE, BLOAD QBasic does not support the cassette device with
BSAVE and BLOAD, and memory locations may be
different.
CALL ABSOLUTE Assembly language programs invoked from BASICA
that have string arguments must be revised for
QBasic because QBasic string descriptors are 4
bytes long. The 4 bytes are the low byte and high
byte of the string length followed by the low
byte and high byte of the string address.
CHAIN QBasic does not allow you to specify a line
number with CHAIN and does not support the ALL,
MERGE, or DELETE options in BASICA.
COMMON, DECLARE QBasic does not allow executable statements to
appear before COMMON and DECLARE statements.
DEFtype If BASICA encounters a variable without an
explicit type (indicated by !, #, &, $, or %), it
uses the default type set by the most recent
DEFtype statement. For example, the type of the
variable IFLAG changes from integer to single
precision in the following BASICA code fragment:
10 DEFINT I
20 PRINT IFLAG
30 DEFSNG I
40 GOTO 20
In QBasic, a variable's type cannot be changed
after it appears in a program.
DIM All arrays in BASICA are dynamic because BASICA
always allocates array storage while a program
runs. In QBasic, DIM can declare either a static
or dynamic array.
DRAW, PLAY DRAW and PLAY statements in BASICA that use
variables or other command strings within command
strings must be modified for QBasic. Use the
VARPTR$ function, which returns a string
representation of the variable's address:
BASICA Statement QBasic Equivalent
---------------- -----------------
DRAW "Xcmdstring$" DRAW "X" + VARPTR$ (cmdstring$)
DRAW "TA = angle" DRAW "TA =" + VARPTR$(angle)
EOF When you direct input from a file to a BASICA
program, EOF(0) returns true at the end of the
input file. In QBasic, EOF(0) returns true after
the next record is read past the end of the input
file. For example, the following program runs in
BASICA, but generates an "Input past end of file"
error message in QBasic:
5 WHILE NOT EOF(0)
10 LINE INPUT ; A$
15 WEND
FIELD When a random-access file is closed in BASICA
with a CLOSE or RESET statement, field variables
retain the last value assigned to them by a GET
statement. In QBasic, all field variables are
reset to null strings.
Additional query words: 6.22 5.00 5.00a 6.00 6.20
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Keywords :
Technology : kbMSDOSSearch kbMSDOS621 kbMSDOS622 kbMSDOS620 kbMSDOS600 kbMSDOS500 kbMSDOS500a
Version : MS-DOS:5.x,6.0,6.2,6.21,6.22
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