Character Representation
ASCII (American Standard Code for Information Interchange)
is
a
widely
used code for representing character data.
It
is
nominally a
7-bit
code, allowing
128
characters
(7F16=1281
0)
ta
be represented. The stan-
dard ASCII
7-bit
character set
is
shawn
in
Table
6-4.
Bits are
numbered
fram 0
(Ieast
significant
bit)
to
6 (most
significant
bit):
7 6 5 4 3 2 1 0
~
Bit number
II[IJ
AS?II cpde
rn
(7-bit
ASCII)
The first 32 codes are reserved for
non-printable
control
characters. intended for
message
formatting
and
print
format
control.
On
the PET, characters are stored
in
ASCII format but
in
anextended
version using eight bits.
With
eight bits normally available, rather than just
seve
n,
up
ta
255
characters can be represented.
Within
compressed BASIC
text
the
8-bit
character codes are interpreted
as
shawn
in
Table
6-3,
where
the eighth
bit
on
signifies a keyword. Eisewhere
in
main memory the
8-bit
character codes are interpreted
as
shawn
in
Appendix
A.
326
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