<s>
The	O
Commodore	B-Operating_System
Plus/4	I-Operating_System
is	O
a	O
home	O
computer	O
released	O
by	O
Commodore	O
International	O
in	O
1984	O
.	O
</s>
<s>
The	O
"	O
Plus/4	B-Operating_System
"	O
name	O
refers	O
to	O
the	O
four-application	O
ROM-resident	O
office	O
suite	O
(	O
word	B-General_Concept
processor	I-General_Concept
,	O
spreadsheet	B-Application
,	O
database	O
,	O
and	O
graphing	B-Application
)	O
;	O
it	O
was	O
billed	O
as	O
"	O
the	O
productivity	O
computer	O
with	O
software	O
built	O
in	O
"	O
.	O
</s>
<s>
Internally	O
,	O
the	O
Plus/4	B-Operating_System
shared	O
the	O
same	O
basic	B-Language
architecture	O
as	O
the	O
lower-end	O
Commodore	B-Operating_System
16	I-Operating_System
and	O
116	O
models	O
,	O
and	O
was	O
able	O
to	O
use	O
software	O
and	O
peripherals	O
designed	O
for	O
them	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
was	O
incompatible	O
with	O
the	O
Commodore	O
64	O
's	O
software	O
and	O
some	O
of	O
its	O
hardware	O
.	O
</s>
<s>
Although	O
the	O
Commodore	O
64	O
was	O
more	O
established	O
,	O
the	O
Plus/4	B-Operating_System
was	O
aimed	O
at	O
the	O
more	O
business	O
oriented	O
part	O
of	O
the	O
personal	O
computer	O
market	O
.	O
</s>
<s>
Companies	O
like	O
Texas	O
Instruments	O
and	O
Timex	O
Corporation	O
were	O
releasing	O
computers	O
that	O
undercut	O
the	O
price	O
of	O
Commodore	O
's	O
PET	B-Device
line	O
.	O
</s>
<s>
Commodore	O
's	O
MOS	B-Architecture
Technology	I-Architecture
division	O
had	O
designed	O
a	O
video	B-General_Concept
chip	I-General_Concept
but	O
could	O
not	O
find	O
any	O
third-party	O
buyers	O
.	O
</s>
<s>
The	O
VIC-20	B-Device
resulted	O
from	O
the	O
confluence	O
of	O
these	O
events	O
and	O
it	O
was	O
introduced	O
in	O
1980	O
at	O
a	O
list	O
price	O
of	O
$299.95	O
.	O
</s>
<s>
The	O
Commodore	O
64	O
,	O
the	O
first	O
64KB	O
computer	O
to	O
sell	O
for	O
under	O
in	O
the	O
US	O
,	O
was	O
another	O
salvo	O
in	O
the	O
price	O
war	O
but	O
it	O
was	O
far	O
more	O
expensive	O
to	O
make	O
than	O
the	O
VIC-20	B-Device
because	O
it	O
used	O
discrete	O
chips	O
for	O
video	O
,	O
sound	O
,	O
and	O
I/O	B-General_Concept
.	O
</s>
<s>
Still	O
,	O
the	O
C64	O
went	O
on	O
to	O
become	O
a	O
best-seller	O
and	O
was	O
selling	O
for	O
$199	O
at	O
the	O
time	O
of	O
the	O
Plus/4	B-Operating_System
'	O
s	O
introduction	O
.	O
</s>
<s>
Rumors	O
spread	O
in	O
late	O
1983	O
of	O
a	O
new	O
computer	O
in	O
1984	O
called	O
the	O
"	O
Commodore	O
444	O
"	O
or	O
"	O
Ted	B-General_Concept
"	O
,	O
with	O
built-in	O
word	O
processing	O
and	O
spreadsheet	B-Application
software	I-Application
,	O
and	O
that	O
it	O
would	O
be	O
one	O
of	O
four	O
new	O
computers	O
that	O
would	O
replace	O
the	O
VIC-20	B-Device
and	O
C64	O
,	O
which	O
the	O
company	O
would	O
discontinue	O
.	O
</s>
<s>
The	O
company	O
's	O
third	O
salvo	O
which	O
,	O
as	O
it	O
turned	O
out	O
,	O
was	O
fired	O
just	O
as	O
most	O
of	O
Commodore	O
's	O
competition	O
was	O
leaving	O
the	O
home	O
computer	O
market	O
was	O
the	O
C116	B-Operating_System
,	O
C16	B-Operating_System
,	O
and	O
264	O
,	O
which	O
became	O
the	O
Plus/4	B-Operating_System
.	O
</s>
<s>
There	O
were	O
also	O
prototypes	O
of	O
a	O
232	O
,	O
basically	O
a	O
version	O
of	O
the	O
Plus/4	B-Operating_System
without	O
the	O
software	O
ROMs	O
,	O
and	O
a	O
V364	O
,	O
which	O
had	O
a	O
numeric	O
keypad	O
and	O
built-in	O
voice	O
synthesis	O
.	O
</s>
<s>
All	O
these	O
computers	O
used	O
a	O
6502	B-General_Concept
compatible	O
MOS	B-General_Concept
7501	I-General_Concept
or	I-General_Concept
8501	I-General_Concept
that	O
was	O
clocked	O
approximately	O
75%	O
faster	O
than	O
the	O
CPUs	O
used	O
in	O
the	O
VIC-20	B-Device
and	O
C64	O
,	O
and	O
a	O
MOS	B-General_Concept
Technology	I-General_Concept
TED	I-General_Concept
all-in-one	O
video	O
,	O
sound	O
,	O
and	O
I/O	B-General_Concept
chip	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
'	O
s	O
design	O
is	O
thus	O
philosophically	O
closer	O
to	O
that	O
of	O
the	O
VIC-20	B-Device
than	O
that	O
of	O
the	O
C64	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
was	O
introduced	O
in	O
June	O
1984	O
and	O
priced	O
at	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
was	O
the	O
flagship	O
computer	O
of	O
the	O
line	O
,	O
featuring	O
of	O
RAM	B-Architecture
while	O
the	O
C16	B-Operating_System
and	O
C116	B-Operating_System
had	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
had	O
built-in	O
software	O
,	O
whereas	O
the	O
others	O
did	O
not	O
.	O
</s>
<s>
Commodore	O
's	O
intent	O
with	O
the	O
Plus/4	B-Operating_System
was	O
not	O
to	O
replace	O
the	O
C64	O
,	O
but	O
to	O
expand	O
the	O
home	O
computer	O
market	O
and	O
sell	O
the	O
Plus/4	B-Operating_System
to	O
users	O
who	O
were	O
more	O
interested	O
in	O
serious	O
applications	O
than	O
in	O
gaming	O
.	O
</s>
<s>
By	O
1984	O
,	O
however	O
,	O
in	O
the	O
US	O
,	O
most	O
of	O
these	O
customers	O
were	O
beginning	O
to	O
switch	O
to	O
the	O
new	O
,	O
low-cost	O
IBM	O
PC	O
compatibles	O
such	O
as	O
the	O
Leading	B-Device
Edge	I-Device
Model	I-Device
D	I-Device
and	O
Tandy	O
1000	O
series	O
.	O
</s>
<s>
Although	O
,	O
like	O
the	O
Commodore	B-Device
B128	I-Device
,	O
Plus/4	B-Operating_System
systems	O
remained	O
available	O
from	O
liquidators	O
for	O
years	O
after	O
its	O
discontinuation	O
,	O
the	O
Plus/4	B-Operating_System
disappeared	O
from	O
Commodore	O
's	O
major	O
markets	O
by	O
1988	O
.	O
</s>
<s>
The	O
TED	B-General_Concept
offered	O
121-color	O
(	O
15	O
colors	O
×	O
8	O
luminance	O
levels	O
+	O
black	O
)	O
video	O
,	O
a	O
palette	B-Data_Structure
matched	O
only	O
by	O
Atari	B-Device
's	I-Device
8-bit	I-Device
computer	I-Device
line	I-Device
and	O
the	O
Enterprise	B-Operating_System
at	O
the	O
time	O
,	O
and	O
320×200	O
video	O
resolution	O
,	O
similar	O
to	O
many	O
computers	O
intended	O
to	O
be	O
capable	O
of	O
connecting	O
to	O
a	O
television	O
.	O
</s>
<s>
The	O
TED	B-General_Concept
chip	O
had	O
identical	O
resolutions	O
and	O
video	O
modes	O
to	O
the	O
VIC-II	O
(	O
bitmap	O
or	O
character	O
graphics	O
which	O
could	O
be	O
high-resolution	O
or	O
multicolor	O
)	O
,	O
but	O
lacked	O
hardware	O
sprites	O
.	O
</s>
<s>
The	O
first	O
eight	O
colors	O
of	O
the	O
TED	B-General_Concept
's	O
palette	B-Data_Structure
are	O
the	O
same	O
as	O
the	O
VIC-II	O
,	O
but	O
colors	O
8-15	O
are	O
different	O
.	O
</s>
<s>
Color	O
memory	O
is	O
integrated	O
into	O
the	O
TED	B-General_Concept
and	O
there	O
is	O
no	O
separate	O
color	O
RAM	B-Architecture
like	O
on	O
the	O
VIC-20	B-Device
and	O
C64	O
.	O
</s>
<s>
Bits	O
0-3	O
of	O
each	O
byte	B-Application
in	O
color	O
RAM	B-Architecture
hold	O
the	O
color	O
value	O
and	O
4-6	O
hold	O
the	O
luminance	O
.	O
</s>
<s>
Bitmap	O
mode	O
is	O
similar	O
to	O
the	O
C64	O
,	O
however	O
in	O
hi-res	O
mode	O
the	O
color	O
RAM	B-Architecture
is	O
used	O
to	O
supply	O
the	O
luminance	O
values	O
for	O
each	O
block	O
(	O
bits	O
0-3	O
the	O
luminance	O
for	O
color	O
0	O
and	O
4-7	O
the	O
luminance	O
for	O
color	O
1	O
)	O
while	O
it	O
is	O
not	O
used	O
at	O
all	O
in	O
C64	O
hi-res	O
graphics	O
.	O
</s>
<s>
In	O
multicolor	O
bitmap	O
mode	O
,	O
the	O
same	O
setup	O
is	O
used	O
,	O
but	O
while	O
on	O
the	O
C64	O
,	O
color	O
RAM	B-Architecture
holds	O
the	O
values	O
for	O
color	O
3	O
,	O
on	O
the	O
Plus/4	B-Operating_System
it	O
instead	O
holds	O
the	O
luminance	O
values	O
for	O
colors	O
1	O
–	O
2	O
.	O
</s>
<s>
Since	O
the	O
Plus/4	B-Operating_System
does	O
not	O
have	O
sprites	O
,	O
games	O
must	O
make	O
use	O
of	O
character	O
graphics	O
for	O
software	O
sprites	O
,	O
like	O
on	O
the	O
VIC-20	B-Device
this	O
tended	O
to	O
cause	O
unintentional	O
color	O
clash	B-Application
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
'	O
s	O
TED	B-General_Concept
has	O
several	O
advantages	O
over	O
C64	O
's	O
VIC+SID	O
.	O
</s>
<s>
All	O
TED	B-General_Concept
registers	O
that	O
are	O
available	O
can	O
be	O
read	O
and	O
written	O
.	O
</s>
<s>
TED	B-General_Concept
may	O
realize	O
the	O
blinking	O
cursor	B-Application
and	O
the	O
characters	O
in	O
the	O
reverse-video	O
mode	O
.	O
</s>
<s>
It	O
may	O
use	O
graphics	O
split	O
by	O
raster	B-General_Concept
interrupt	I-General_Concept
and	O
show	O
pictures	O
at	O
320x248	O
resolution	O
.	O
</s>
<s>
In	O
addition	O
,	O
the	O
TED	B-General_Concept
has	O
16	O
address	O
lines	O
,	O
thus	O
it	O
can	O
"	O
see	O
"	O
the	O
entire	O
memory	O
space	O
of	O
the	O
computer	O
unlike	O
the	O
VIC-II	O
.	O
</s>
<s>
The	O
video	O
buffers	O
may	O
thus	O
be	O
placed	O
anywhere	O
in	O
memory	O
and	O
there	O
are	O
no	O
mirrors	O
of	O
the	O
character	O
ROM	B-Device
to	O
get	O
in	O
the	O
way	O
like	O
on	O
the	O
C64	O
.	O
</s>
<s>
Commodore	O
released	O
a	O
high-speed	O
floppy	B-Device
disk	I-Device
drive	I-Device
for	O
the	O
Plus/4	B-Operating_System
,	O
the	O
Commodore	B-Device
1551	I-Device
,	O
which	O
offered	O
much	O
better	O
performance	O
than	O
the	O
C64/1541	O
combination	O
because	O
it	O
used	O
a	O
parallel	O
interface	O
rather	O
than	O
a	O
serial	O
bus	O
.	O
</s>
<s>
The	O
1551	O
plugged	O
into	O
the	O
cartridge	B-Protocol
port	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
had	O
a	O
built-in	O
MOS	B-Architecture
Technology	I-Architecture
6551	I-Architecture
UART	O
chip	O
that	O
could	O
perform	O
up	O
to	O
,	O
unlike	O
the	O
C64	O
,	O
which	O
emulated	O
the	O
6551	B-Architecture
chip	O
in	O
software	O
.	O
</s>
<s>
This	O
allowed	O
the	O
Plus/4	B-Operating_System
to	O
use	O
high-speed	O
modems	B-Application
without	O
additional	O
hardware	O
or	O
software	O
tricks	O
(	O
the	O
C64	O
required	O
specially	O
written	O
software	O
to	O
operate	O
at	O
)	O
,	O
at	O
a	O
time	O
when	O
300	O
-	O
or	O
1200-bit/s	O
modems	B-Application
were	O
more	O
common	O
and	O
Commodore	O
never	O
released	O
a	O
2400-bit/s	O
modem	B-Application
so	O
this	O
feature	O
went	O
largely	O
unnoticed	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
'	O
s	O
serial	O
port	O
is	O
the	O
standard	O
Commodore	O
user	O
port	O
used	O
since	O
the	O
PET	B-Device
,	O
featuring	O
TTL	B-General_Concept
voltage	O
which	O
is	O
incompatible	O
with	O
RS-232	O
.	O
</s>
<s>
This	O
requires	O
a	O
voltage	O
converter	O
to	O
use	O
modems	B-Application
or	O
other	O
serial	O
devices	O
from	O
non-Commodore	O
vendors	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
keyboard	O
had	O
a	O
separately	O
placed	O
directional	O
"	O
diamond	O
"	O
of	O
four	O
cursor	B-Application
keys	O
,	O
presumably	O
more	O
intuitive	O
to	O
use	O
than	O
the	O
VIC	O
's	O
and	O
C64	O
's	O
two	O
shifted	O
cursor	B-Application
keys	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
also	O
revived	O
the	O
built-in	O
machine	B-General_Concept
language	I-General_Concept
monitor	I-General_Concept
from	O
the	O
PET	B-Device
days	O
,	O
a	O
feature	O
missing	O
on	O
the	O
VIC-20	B-Device
and	O
C64	O
.	O
</s>
<s>
RAM	B-Architecture
:	O
,	O
of	O
which	O
nearly	O
(	O
60671	O
bytes	B-Application
)	O
is	O
available	O
to	O
BASIC	B-Language
users	O
.	O
</s>
<s>
ROM	B-Device
:	O
including	O
Commodore	B-Language
BASIC	I-Language
3.5	I-Language
,	O
a	O
machine	B-General_Concept
code	I-General_Concept
monitor	I-General_Concept
,	O
and	O
TRI-Micro	O
'	O
s	O
"	O
3	O
Plus	O
1	O
"	O
(	O
word	B-General_Concept
processor	I-General_Concept
,	O
spreadsheet	B-Application
,	O
database	O
,	O
graphing	B-Application
)	O
.	O
</s>
<s>
It	O
is	O
possible	O
to	O
add	O
up	O
to	O
more	O
ROM	B-Device
with	O
cartridges	B-Protocol
.	O
</s>
<s>
Text	O
mode	O
:	O
40×25	O
characters	O
(	O
PETSCII	B-Protocol
)	O
.	O
</s>
<s>
I/O	B-Architecture
ports	I-Architecture
:	O
</s>
<s>
Tape	O
connector	O
(	O
for	O
Commodore	B-Device
1531	I-Device
Datassette	B-Device
with	O
;	O
incompatible	O
with	O
C64	O
,	O
although	O
adapters	O
allowing	O
the	O
machine	O
to	O
use	O
earlier	O
and	O
aftermarket	O
datasettes	B-Device
were	O
common	O
.	O
)	O
</s>
<s>
The	O
power	O
connector	O
is	O
compatible	O
with	O
C64	O
power	O
supplies	O
in	O
some	O
Plus/4s	B-Operating_System
and	O
takes	O
the	O
same	O
9V	O
AC	O
and	O
5V	O
DC	O
voltages	O
,	O
but	O
uses	O
a	O
non-standard	O
"	O
Square	O
DIN	O
"	O
plug	O
,	O
like	O
the	O
C128	O
,	O
in	O
most	O
Plus/4s	B-Operating_System
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
'	O
s	O
memory	B-General_Concept
map	I-General_Concept
,	O
which	O
used	O
bank	B-General_Concept
switching	I-General_Concept
far	O
more	O
extensively	O
than	O
the	O
C64	O
,	O
gave	O
it	O
a	O
56%	O
larger	O
amount	O
of	O
user-accessible	O
memory	O
than	O
the	O
C64	O
for	O
programming	O
in	O
BASIC	B-Language
,	O
and	O
its	O
BASIC	B-Language
programming	I-Language
language	I-Language
was	O
vastly	O
improved	O
,	O
adding	O
sound	O
and	O
graphics	O
commands	O
as	O
well	O
as	O
looping	O
commands	O
that	O
improved	O
program	B-Language
structure	I-Language
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
does	O
not	O
have	O
the	O
Restore	O
key	O
on	O
the	O
VIC	O
and	O
C64	O
,	O
but	O
a	O
similar	O
function	O
may	O
be	O
achieved	O
by	O
holding	O
down	O
Run/Stop	O
and	O
pressing	O
the	O
reset	O
button	O
.	O
</s>
<s>
This	O
will	O
reboot	O
the	O
computer	O
into	O
the	O
machine	B-General_Concept
language	I-General_Concept
monitor	I-General_Concept
,	O
but	O
any	O
BASIC	B-Language
programs	O
in	O
memory	O
will	O
be	O
left	O
intact	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
contains	O
an	O
Easter	O
egg	O
.	O
</s>
<s>
While	O
the	O
C64	O
had	O
the	O
advertised	O
of	O
RAM	B-Architecture
installed	O
,	O
only	O
about	O
was	O
available	O
for	O
BASIC	B-Language
programs	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
'	O
s	O
BASIC	B-Language
V3.5	O
made	O
available	O
,	O
aided	O
by	O
its	O
memory	B-General_Concept
map	I-General_Concept
that	O
swapped	O
the	O
ROMs	O
in	O
and	O
out	O
of	O
memory	O
as	O
needed	O
,	O
and	O
that	O
placed	O
the	O
memory	B-Architecture
mapped	I-Architecture
I/O	I-Architecture
registers	O
,	O
which	O
all	O
6502-based	O
computers	O
have	O
to	O
use	O
,	O
at	O
the	O
top	O
of	O
memory	O
( $FD00	O
)	O
,	O
while	O
in	O
the	O
C64	O
they	O
had	O
been	O
located	O
at	O
the	O
much	O
lower	O
address	O
$D000	O
.	O
</s>
<s>
On	O
the	O
C64	O
,	O
a	O
program	O
was	O
able	O
to	O
swap	O
out	O
the	O
ROMs	O
and	O
the	O
I/O	B-General_Concept
registers	O
manually	O
and	O
thus	O
gain	O
access	O
to	O
the	O
full	O
,	O
but	O
this	O
was	O
not	O
compatible	O
with	O
BASIC	B-Language
on	O
that	O
machine	O
;	O
on	O
the	O
Plus/4	B-Operating_System
,	O
on	O
the	O
other	O
hand	O
,	O
most	O
of	O
the	O
ROM	B-Device
area	O
was	O
automatically	O
switched	O
out	O
when	O
not	O
needed	O
,	O
rendering	O
the	O
RAM	B-Architecture
existing	O
at	O
the	O
same	O
addresses	O
accessible	O
for	O
BASIC	B-Language
programs	O
.	O
</s>
<s>
The	O
BASIC	B-Language
program	O
area	O
on	O
the	O
Plus/4	B-Operating_System
begins	O
at	O
$1000	O
,	O
but	O
the	O
BASIC	B-Language
ROM	B-Device
starts	O
at	O
$8000	O
so	O
the	O
automatic	O
switching	O
of	O
the	O
OS	O
ROMs	O
is	O
not	O
initiated	O
unless	O
a	O
BASIC	B-Language
program	O
grows	O
big	O
enough	O
to	O
reach	O
$8000	O
,	O
or	O
28K	O
in	O
size	O
.	O
</s>
<s>
Since	O
RAM	B-Architecture
on	O
the	O
C16	B-Operating_System
never	O
exceeds	O
the	O
$8000	O
line	O
,	O
banking	O
does	O
not	O
occur	O
on	O
that	O
machine	O
.	O
</s>
<s>
As	O
on	O
the	O
C64	O
,	O
writing	O
to	O
the	O
ROM	B-Device
areas	O
will	O
alter	O
the	O
RAM	B-Architecture
underneath	O
.	O
</s>
<s>
The	O
registers	O
at	O
$	O
FDD0-	O
$FDDF	O
contain	O
the	O
ROM	B-Device
configuration	O
for	O
the	O
machine	O
,	O
which	O
normally	O
has	O
the	O
BASIC	B-Language
and	O
kernal	O
ROMs	O
enabled	O
.	O
</s>
<s>
The	O
ROM	B-Device
configuration	O
is	O
adjusted	O
by	O
writing	O
to	O
the	O
registers	O
(	O
the	O
value	O
is	O
irrelevant	O
)	O
.	O
</s>
<s>
$FDD0	O
enables	O
or	O
disables	O
BASIC$	O
,	O
FDD1	O
the	O
low	O
function	O
ROM$	O
,	O
FDD2	O
the	O
low	O
cartridge	B-Protocol
ROM$	O
,	O
FDD3	O
is	O
unused$	O
,	O
FDD4	O
the	O
kernal$	O
,	O
FDD5	O
the	O
high	O
function	O
ROM	B-Device
,	O
and	O
$FDD6	O
the	O
high	O
cartridge	B-Protocol
ROM	B-Device
.	O
</s>
<s>
The	O
upper	O
portion	O
of	O
the	O
kernal	O
ROM	B-Device
at	O
$	O
FC00-	O
$FCFF	O
is	O
always	O
enabled	O
no	O
matter	O
what	O
the	O
memory	O
configuration	O
,	O
as	O
are	O
the	O
I/O	B-General_Concept
registers	O
.	O
</s>
<s>
Furthermore	O
,	O
the	O
registers	O
at	O
$	O
FF3E-	O
$FF3F	O
if	O
written	O
to	O
will	O
bank	O
out	O
(	O
or	O
in	O
)	O
all	O
ROMs	O
currently	O
enabled	O
via	O
the	O
ROM	B-Device
configuration	O
at	O
$	O
FDD0-	O
$FDDF	O
excepting	O
$	O
FC00-	O
$FCFF	O
;	O
this	O
is	O
done	O
by	O
BASIC	B-Language
automatically	O
to	O
read	O
program	O
text	O
above	O
$8000	O
.	O
</s>
<s>
BASIC	B-Language
3.5	O
added	O
all	O
of	O
BASIC	B-Language
4.0	O
'	O
s	O
disk	O
commands	O
as	O
well	O
as	O
sound	O
and	O
graphics	O
functions	O
to	O
support	O
the	O
TED	B-General_Concept
,	O
additional	O
programming	O
features	O
,	O
and	O
statements	O
to	O
allow	O
structured	B-Language
programming	I-Language
.	O
</s>
<s>
While	O
BASIC	B-Language
2.0	I-Language
was	O
8K	O
in	O
size	O
and	O
BASIC	B-Language
4.0	O
12K	O
,	O
BASIC	B-Language
3.5	O
ballooned	O
to	O
20K	O
in	O
size	O
,	O
as	O
big	O
as	O
the	O
entire	O
set	O
of	O
OS	O
ROMs	O
in	O
the	O
VIC-20	B-Device
and	O
C64	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
,	O
unlike	O
the	O
C64	O
,	O
was	O
equipped	O
with	O
a	O
ROM-resident	O
application	O
suite	O
.	O
</s>
<s>
It	O
was	O
,	O
however	O
,	O
completely	O
inadequate	O
for	O
the	O
Plus/4	B-Operating_System
'	O
s	O
originally	O
intended	O
market	O
of	O
business	O
and	O
professional	O
users	O
.	O
</s>
<s>
In	O
an	O
otherwise	O
largely	O
favorable	O
review	O
of	O
the	O
computer	O
,	O
John	O
J	O
.	O
Anderson	O
of	O
Creative	B-General_Concept
Computing	I-General_Concept
wrote	O
"	O
I	O
would	O
guess	O
that	O
the	O
applications	O
were	O
whipped	O
up	O
in	O
a	O
great	O
hurry	O
...	O
</s>
<s>
The	O
Transactor	O
stated	O
,	O
"	O
The	O
word	B-General_Concept
processor	I-General_Concept
is	O
barely	O
that	O
,	O
the	O
data	O
base	O
defiles	O
the	O
name	O
,	O
and	O
the	O
spreadsheet	B-Application
has	O
little	O
spread	O
"	O
.	O
</s>
<s>
BYTE	B-Application
called	O
the	O
built-in	O
software	O
"	O
just	O
a	O
tiny	O
bit	O
better	O
than	O
bad	O
"	O
,	O
noting	O
that	O
a	O
Commodore	O
64	O
with	O
Multiplan	B-Device
and	O
other	O
third-party	O
software	O
would	O
be	O
cheaper	O
and	O
much	O
more	O
powerful	O
.	O
</s>
<s>
The	O
magazine	O
stated	O
that	O
the	O
computer	O
"	O
should	O
have	O
been	O
called	O
not	O
the	O
Plus	B-Operating_System
4	I-Operating_System
,	O
but	O
the	O
Minus	O
60	O
"	O
.	O
</s>
<s>
INFO	O
warned	O
that	O
users	O
who	O
wanted	O
to	O
use	O
the	O
computer	O
"	O
for	O
serious	O
'	O
productive	O
 '	O
work	O
,	O
you	O
are	O
in	O
deep	O
trouble	O
with	O
the	O
PLUS/4	B-Operating_System
"	O
because	O
of	O
the	O
poor	O
software	O
,	O
and	O
unlikelihood	O
that	O
better	O
third-party	O
replacements	O
would	O
be	O
available	O
.	O
</s>
<s>
Since	O
IBM	O
compatibles	O
were	O
quickly	O
dominating	O
the	O
small	O
business	O
market	O
,	O
the	O
Plus/4	B-Operating_System
had	O
no	O
realistic	O
chance	O
of	O
succeeding	O
in	O
its	O
intended	O
use	O
.	O
</s>
<s>
Thus	O
,	O
tape-based	O
home	O
users	O
,	O
the	O
only	O
users	O
who	O
might	O
still	O
have	O
been	O
interested	O
in	O
the	O
Plus/4	B-Operating_System
'	O
s	O
less-capable	O
but	O
built-in	O
and	O
instantly	O
ready	O
software	O
,	O
were	O
shut	O
out	O
from	O
the	O
package	O
.	O
</s>
<s>
The	O
keyboard	O
on	O
the	O
Plus/4	B-Operating_System
was	O
different	O
from	O
the	O
keyboards	O
of	O
previous	O
Commodore	O
machines	O
and	O
also	O
its	O
sibling	O
the	O
C16	B-Operating_System
;	O
this	O
was	O
due	O
to	O
cost	O
saving	O
measures	O
resulting	O
from	O
the	O
need	O
to	O
retool	O
for	O
Plus/4	B-Operating_System
production	O
,	O
while	O
the	O
C16	B-Operating_System
could	O
use	O
the	O
existing	O
C64	O
tooling	O
due	O
to	O
an	O
identical	O
case	O
design	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
'	O
s	O
serial	O
,	O
user	O
,	O
and	O
video	O
ports	O
were	O
compatible	O
with	O
the	O
C64	O
,	O
but	O
the	O
Datasette	B-Device
port	O
was	O
changed	O
,	O
rendering	O
previous	O
units	O
incompatible	O
without	O
third-party	O
adapters	O
that	O
only	O
became	O
available	O
later	O
.	O
</s>
<s>
Since	O
most	O
of	O
these	O
interfaces	O
connected	O
to	O
the	O
Datasette	B-Device
port	O
to	O
get	O
+5	O
volts	O
for	O
power	O
,	O
they	O
were	O
incompatible	O
with	O
the	O
Plus/4	B-Operating_System
unless	O
the	O
user	O
modified	O
the	O
interface	O
and	O
risked	O
voiding	O
the	O
warranty	O
.	O
</s>
<s>
Additionally	O
,	O
with	O
the	O
Plus/4	B-Operating_System
,	O
Commodore	O
abandoned	O
the	O
common	O
Atari-style	O
joystick	B-Device
ports	O
used	O
on	O
the	O
C64	O
,	O
replacing	O
them	O
with	O
a	O
proprietary	B-Device
mini-DIN	O
port	O
that	O
was	O
said	O
to	O
be	O
less	O
prone	O
to	O
emit	O
RF	O
interference	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
does	O
not	O
support	O
analog	O
devices	O
via	O
the	O
joyports	O
like	O
the	O
C64	O
mouse	B-Device
,	O
making	O
programs	O
with	O
a	O
GUI	B-Application
such	O
as	O
GEOS	B-Device
less	O
friendly	O
to	O
use	O
.	O
</s>
<s>
However	O
,	O
there	O
is	O
an	O
unfinished	O
project	O
that	O
allows	O
the	O
use	O
of	O
a	O
standard	O
IBM	O
PC	O
compatible	O
serial	B-Device
mouse	I-Device
.	O
</s>
<s>
While	O
the	O
Plus/4	B-Operating_System
'	O
s	O
CPU	O
could	O
run	O
about	O
75%	O
faster	O
than	O
the	O
C64	O
's	O
,	O
the	O
computer	O
was	O
still	O
designed	O
with	O
a	O
shared	B-General_Concept
memory	I-General_Concept
architecture	O
,	O
in	O
which	O
screen	O
data	O
resided	O
in	O
main	O
memory	O
.	O
</s>
<s>
This	O
means	O
that	O
the	O
video	B-General_Concept
chip	I-General_Concept
has	O
to	O
access	O
the	O
memory	O
while	O
it	O
is	O
displaying	O
the	O
picture	O
,	O
in	O
effect	O
slowing	O
down	O
the	O
CPU	O
to	O
less	O
than	O
half	O
its	O
full	O
speed	O
in	O
this	O
screen	O
area	O
.	O
</s>
<s>
Only	O
during	O
those	O
periods	O
when	O
the	O
video	B-General_Concept
chip	I-General_Concept
is	O
displaying	O
the	O
screen	O
border	O
or	O
putting	O
out	O
the	O
horizontal	O
and	O
vertical	O
retrace	O
signals	O
is	O
the	O
CPU	O
able	O
to	O
run	O
at	O
full	O
speed	O
.	O
</s>
<s>
This	O
means	O
that	O
,	O
on	O
average	O
,	O
with	O
standard	O
40x25	O
screen	O
the	O
Plus/4	B-Operating_System
'	O
s	O
CPU	O
runs	O
only	O
about	O
15%	O
faster	O
than	O
that	O
of	O
the	O
C64	O
.	O
</s>
<s>
However	O
,	O
as	O
mentioned	O
the	O
Plus/4	B-Operating_System
can	O
be	O
75%	O
faster	O
than	O
a	O
C64	O
when	O
using	O
screen	O
blanking	O
mode	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
'	O
s	O
PAL	B-Language
model	O
may	O
also	O
be	O
switched	O
to	O
NTSC	O
mode	O
by	O
disabling	O
the	O
screen	O
which	O
sets	O
the	O
CPU	O
frequency	O
to	O
2.22MHz	O
(	O
this	O
is	O
115%	O
faster	O
than	O
C64	O
's	O
maximum	O
speed	O
)	O
.	O
</s>
<s>
So	O
a	O
Plus/4	B-Operating_System
(	O
PAL	B-Language
)	O
is	O
one	O
of	O
the	O
fastest	O
6502	B-General_Concept
based	O
computers	O
for	O
raw	O
calculations	O
.	O
</s>
<s>
This	O
is	O
true	O
for	O
programs	O
in	O
machine	O
code	O
but	O
BASIC	B-Language
3.5	O
is	O
slightly	O
slower	O
than	O
BASIC	B-Language
2.0	I-Language
due	O
to	O
its	O
greater	O
size	O
,	O
and	O
performance	O
slows	O
down	O
further	O
when	O
programs	O
cross	O
over	O
the	O
$8000	O
line	O
because	O
the	O
BASIC	B-Language
ROM	B-Device
has	O
to	O
be	O
switched	O
out	O
to	O
read	O
BASIC	B-Language
program	O
text	O
.	O
</s>
<s>
The	O
NTSC	O
model	O
of	O
Plus/4	B-Operating_System
is	O
about	O
10%	O
slower	O
than	O
the	O
PAL	B-Language
model	O
displaying	O
a	O
standard	O
screen	O
but	O
slightly	O
faster	O
with	O
screen	O
blank	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
also	O
suffered	O
serious	O
reliability	O
problems	O
due	O
to	O
the	O
TED	B-General_Concept
chip	O
,	O
which	O
was	O
one	O
of	O
the	O
first	O
ICs	O
MOS	O
developed	O
using	O
the	O
newer	O
,	O
lower	O
power	O
HMOS	O
process	O
.	O
</s>
<s>
MOS	O
had	O
considerable	O
difficulty	O
getting	O
it	O
to	O
work	O
reliably	O
and	O
TED	B-General_Concept
chips	O
and	O
the	O
7501	O
CPU	O
consequently	O
had	O
a	O
high	O
failure	O
rate	O
.	O
</s>
<s>
Autofire-capable	O
joysticks	B-Device
and	O
improperly	O
constructed	O
9-pin	O
adapters	O
have	O
also	O
been	O
blamed	O
for	O
damaging	O
TED	B-General_Concept
chips	O
.	O
</s>
<s>
The	O
C16	B-Operating_System
had	O
fewer	O
reliability	O
problems	O
than	O
the	O
Plus/4	B-Operating_System
due	O
to	O
a	O
simpler	O
design	O
with	O
fewer	O
ICs	O
and	O
lower	O
heat	O
output	O
,	O
as	O
well	O
as	O
more	O
room	O
inside	O
the	O
case	O
for	O
heat	O
to	O
disperse	O
.	O
</s>
<s>
Like	O
with	O
the	O
C64	O
,	O
the	O
Plus/4	B-Operating_System
also	O
used	O
an	O
unreliable	O
power	O
supply	O
that	O
was	O
prone	O
to	O
overheating	O
and	O
damaging	O
components	O
in	O
the	O
machine	O
.	O
</s>
<s>
This	O
made	O
upgrading	O
to	O
the	O
Plus/4	B-Operating_System
from	O
the	O
VIC-20	B-Device
or	O
C64	O
more	O
expensive	O
,	O
since	O
the	O
user	O
in	O
many	O
cases	O
would	O
have	O
to	O
buy	O
new	O
peripherals	O
in	O
addition	O
to	O
the	O
new	O
computer	O
.	O
</s>
<s>
It	O
also	O
made	O
the	O
Plus/4	B-Operating_System
less	O
attractive	O
to	O
new	O
buyers	O
,	O
since	O
VIC	O
and	O
C64	O
peripherals	O
were	O
more	O
plentiful	O
and	O
less	O
expensive	O
than	O
their	O
Plus/4	B-Operating_System
counterparts	O
.	O
</s>
<s>
The	O
street	O
price	O
for	O
a	O
complete	O
C64	O
system	O
was	O
lower	O
than	O
that	O
of	O
a	O
comparable	O
system	O
based	O
on	O
the	O
Plus/4	B-Operating_System
.	O
</s>
<s>
The	O
press	O
mocked	O
the	O
Plus/4	B-Operating_System
.	O
</s>
<s>
'	O
s	O
Gazette	O
compared	O
the	O
Plus/4	B-Operating_System
to	O
"	O
The	O
Emperor	O
's	O
New	O
Clothes	O
"	O
.	O
</s>
<s>
Even	O
a	O
defender	O
of	O
the	O
machine	O
acknowledged	O
that	O
the	O
Plus/4	B-Operating_System
was	O
expensive	O
compared	O
to	O
the	O
C64	O
,	O
and	O
that	O
the	O
built-in	O
applications	O
 '	O
quality	O
was	O
poor	O
.	O
</s>
<s>
Steve	O
Leininger	O
,	O
the	O
designer	O
of	O
the	O
Tandy	B-Device
TRS-80	I-Device
Model	O
I	O
,	O
said	O
in	O
July	O
1984	O
that	O
the	O
new	O
computer	O
's	O
incompatibility	O
with	O
C64	O
software	O
"	O
makes	O
you	O
wonder	O
"	O
.	O
</s>
<s>
He	O
added	O
"	O
It	O
's	O
a	O
little	O
on	O
the	O
spooky	O
side	O
"	O
,	O
unfavorably	O
comparing	O
the	O
Plus/4	B-Operating_System
to	O
the	O
Apple	O
IIc	O
's	O
compatibility	O
with	O
the	O
tens	O
of	O
thousands	O
of	O
Apple	O
II	O
software	O
packages	O
.	O
</s>
<s>
Another	O
problem	O
that	O
kept	O
the	O
Plus/4	B-Operating_System
from	O
selling	O
was	O
that	O
even	O
though	O
the	O
three	O
machines	O
(	O
116	O
,	O
C16	B-Operating_System
and	O
Plus/4	B-Operating_System
)	O
were	O
all	O
compatible	O
with	O
one	O
another	O
,	O
developers	O
tended	O
to	O
write	O
programs	O
for	O
the	O
lowest	O
common	O
denominator	O
in	O
a	O
computer	O
family	O
.	O
</s>
<s>
So	O
as	O
not	O
to	O
alienate	O
buyers	O
of	O
the	O
C116	B-Operating_System
and	O
C16	B-Operating_System
,	O
which	O
were	O
intended	O
to	O
be	O
the	O
largest	O
selling	O
machines	O
in	O
this	O
series	O
,	O
most	O
software	O
was	O
designed	O
to	O
run	O
in	O
and	O
the	O
extra	O
memory	O
on	O
the	O
Plus/4	B-Operating_System
was	O
not	O
as	O
widely	O
supported	O
as	O
it	O
could	O
have	O
been	O
.	O
</s>
<s>
Plus/4	B-Operating_System
software	O
development	O
in	O
North	O
America	O
was	O
mostly	O
the	O
domain	O
of	O
obscure	O
companies	O
who	O
sold	O
products	O
via	O
mail	O
order	O
,	O
similar	O
to	O
other	O
computers	O
like	O
the	O
TRS-80	B-Device
CoCo	I-Device
that	O
did	O
not	O
have	O
support	O
from	O
major	O
developers	O
.	O
</s>
<s>
Since	O
the	O
Plus/4	B-Operating_System
accounted	O
for	O
most	O
North	O
American	O
sales	O
,	O
NTSC	O
software	O
was	O
usually	O
designed	O
to	O
support	O
64K	O
and	O
disk	O
drives	O
unlike	O
in	O
Europe	O
where	O
software	O
was	O
most	O
often	O
distributed	O
on	O
cassette	O
and	O
designed	O
to	O
support	O
a	O
16K	O
machine	O
.	O
</s>
<s>
Of	O
these	O
,	O
400,000	O
were	O
Plus/4s	B-Operating_System
with	O
most	O
of	O
the	O
remainder	O
being	O
C16s	O
.	O
</s>
<s>
Approximately	O
50,000	O
were	O
C116s	B-Operating_System
,	O
with	O
about	O
43,000	O
of	O
those	O
being	O
sold	O
in	O
Germany	O
,	O
and	O
the	O
Plus/4	B-Operating_System
accounted	O
for	O
about	O
60%	O
-70	O
%	O
of	O
North	O
American	O
sales	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
was	O
later	O
used	O
in	O
Denmark	O
,	O
as	O
part	O
of	O
a	O
bundled	O
product	O
from	O
the	O
then-national	O
telecommunications	O
company	O
(	O
now	O
TDC	O
A/S	O
)	O
to	O
help	O
hearing-impaired	O
people	O
communicate	O
over	O
telephone	O
lines	O
.	O
</s>
<s>
Outgoing	O
calls	O
were	O
made	O
from	O
the	O
Plus/4	B-Operating_System
via	O
modem	B-Application
to	O
a	O
call	O
center	O
where	O
a	O
service	O
assistant	O
would	O
read	O
the	O
written	O
input	O
from	O
the	O
user	O
,	O
call	O
the	O
other	O
party	O
and	O
read	O
the	O
text	O
aloud	O
.	O
</s>
<s>
Vice	O
versa	O
,	O
incoming	O
calls	O
could	O
be	O
made	O
from	O
other	O
users	O
to	O
the	O
call	O
center	O
,	O
who	O
would	O
dial	O
the	O
Plus/4	B-Operating_System
modem	B-Application
.	O
</s>
<s>
A	O
strobe	O
light	O
connected	O
to	O
the	O
Plus/4	B-Operating_System
would	O
notify	O
the	O
hearing	O
impaired	O
about	O
the	O
incoming	O
call	O
.	O
</s>
<s>
The	O
Plus/4	B-Operating_System
enjoyed	O
lasting	O
popularity	O
in	O
Hungary	O
due	O
to	O
CBM	O
's	O
decision	O
to	O
saturate	O
the	O
Central	O
European	O
market	O
with	O
the	O
failed	O
product	O
at	O
a	O
greatly	O
reduced	O
price	O
.	O
</s>
<s>
Most	O
of	O
the	O
developers	O
of	O
the	O
Plus/4	B-Operating_System
also	O
worked	O
on	O
the	O
later	O
Commodore	B-Device
128	I-Device
project	O
,	O
which	O
was	O
much	O
more	O
successful	O
.	O
</s>
<s>
Even	O
as	O
the	O
Plus/4	B-Operating_System
and	O
C16	B-Operating_System
began	O
shipping	O
,	O
Compute	O
!	O
</s>
<s>
Their	O
shortcomings	O
were	O
the	O
inspiration	O
for	O
the	O
Commodore	B-Device
128	I-Device
series	O
as	O
,	O
urged	O
on	O
by	O
the	O
computer	O
press	O
,	O
the	O
designers	O
calculated	O
that	O
if	O
they	O
created	O
a	O
computer	O
that	O
was	O
compatible	O
with	O
the	O
C64	O
that	O
ultimately	O
management	O
and	O
marketing	O
could	O
not	O
damage	O
the	O
C64	O
software	O
base	O
(	O
much	O
)	O
in	O
spite	O
of	O
how	O
they	O
were	O
to	O
take	O
the	O
product	O
to	O
market	O
.	O
</s>
