Radio Shack TRS-80 Trsdos & Disk Basic Reference Manual page 92

DISK BASIC
Error Messages
When
an
error occurs,
DISK BASIC
"spells
out" the
full
error
message, not
just
the abbreviation. This saves
you
from having
to
look
it
up.
Example:
error<i4)
mma
DISK BASIC
responds
with:
OUT OF
STRING SPACE
Note:
The
ERROR
function,
used
to
simulate error conditions,
will
work
only with non-disk error codes.
&H
and
&O
(hex
and
octal constants)
Often
it is
convenient to use
hex
(base 16) or octal (base
8)
constants rather than
their
decimal counterparts.
For
example,
memory
addresses
and byte
values
are easier
to
manipulate
in
hex
form.
&H
and
&0
let
you
introduce such constants
into
your
program.
&H
and
&O
are
used
as
prefixes for the
numerals
that
immediately
follow
them:
&Hdddd
where
dddd
&Oddddd
where
ddddd
is
a
1
to
4
digit
sequence
composed
of
hexadecimal numerals
0,
1
,
. . .
9,A,B,
.
.
.
,F
is
a
sequence of
octal
numerals
0,
1
, .
.
.,7.
and
&Oddddd< =
1
77777 decimal.
Note:
The
O
can be omitted from
the
prefix
&0.
Therefore
&Oddddd=&ddddd.
The
constants
always
represent signed
integers.
Therefore any hex number
greater
than
&H7FFF,
or
any
octal
number
greater
than
&077777,
will
be
interpreted
as a
negative
quantity.
The
following
table
illustrates this:
Octal
Hex
Decimal
&1
&H1
1
&2
&H2
2
&77777
&H7FFF
32767
&
100000
&H8000
-32768
&1
00001
&H8001
-32767
&100002
&H8002
-32766
&177776
&HFFFE
-2
&177777
&HFFFF
-1
a
7-6