Important Notice
The pages on this site contain documentation for very old MS-DOS software,
purely for historical purposes.
If you're looking for up-to-date documentation, particularly for programming,
you should not rely on the information found here, as it will be woefully
out of date.
Differences from BASICA
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The following keywords behave differently in QBasic than in BASICA:
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.
See Also ◄Converting BASICA Programs► ◄Unsupported Keywords►
◄Version Differences►