<s>
This	O
was	O
due	O
to	O
the	O
use	O
of	O
ASICs	O
for	O
graphics	O
and	O
sound	O
which	O
took	O
workload	O
away	O
from	O
the	O
CPU	O
,	O
an	O
extensive	O
implementation	O
of	O
ANSI	B-Language
BASIC	I-Language
and	O
a	O
bank	B-General_Concept
switching	I-General_Concept
system	O
to	O
allow	O
for	O
larger	O
amounts	O
of	O
RAM	B-Architecture
than	O
the	O
Z80	B-General_Concept
natively	O
supported	O
.	O
</s>
<s>
Its	O
two	O
variants	O
are	O
the	O
Enterprise	B-Operating_System
64	I-Operating_System
,	O
with	O
64	O
kilobytes	O
of	O
Random	B-Architecture
Access	I-Architecture
Memory	I-Architecture
(	O
RAM	B-Architecture
)	O
,	O
and	O
the	O
Enterprise	B-Operating_System
128	I-Operating_System
,	O
with	O
128	O
KB	O
of	O
RAM	B-Architecture
.	O
</s>
<s>
The	O
Enterprise	O
has	O
a	O
4	O
megahertz	O
(	O
MHz	O
)	O
Z80	B-General_Concept
Central	B-General_Concept
processing	I-General_Concept
unit	I-General_Concept
(	O
CPU	O
)	O
,	O
64	O
KB	O
(	O
65,536	O
bytes	O
)	O
or	O
128	O
KB	O
of	O
RAM	B-Architecture
,	O
and	O
32	O
KB	O
(	O
32,768	O
bytes	O
)	O
of	O
internal	O
read-only	B-Device
memory	I-Device
(	O
ROM	B-Device
)	O
that	O
contains	O
the	O
EXOS	O
operating	O
system	O
and	O
a	O
screen	O
editor	O
/	O
word	O
processor	O
.	O
</s>
<s>
The	O
BASIC	B-Language
programming	I-Language
language	I-Language
was	O
supplied	O
on	O
a	O
16	O
KB	O
ROM	B-Device
module	O
.	O
</s>
<s>
They	O
are	O
named	O
"	O
Nick	O
"	O
and	O
"	O
Dave	O
"	O
after	O
their	O
designers	O
,	O
Nick	O
Toop	O
,	O
who	O
had	O
previously	O
worked	O
on	O
the	O
Acorn	B-Device
Atom	I-Device
,	O
and	O
Dave	O
Woodfield	O
.	O
</s>
<s>
"	O
Nick	O
"	O
manages	O
graphics	O
,	O
while	O
"	O
Dave	O
"	O
handles	O
sound	O
and	O
memory	O
paging	O
(	O
bank	B-General_Concept
switching	I-General_Concept
)	O
.	O
</s>
<s>
A	O
bank	B-General_Concept
switching	I-General_Concept
scheme	O
allows	O
the	O
memory	O
to	O
be	O
expanded	O
to	O
a	O
maximum	O
of	O
4	O
megabytes	O
(	O
4,194,304	O
bytes	O
)	O
.	O
</s>
<s>
The	O
highest	O
2	O
address	O
lines	O
from	O
the	O
Z80	B-General_Concept
are	O
used	O
to	O
select	O
one	O
of	O
the	O
four	O
8-bit	O
Page	O
Registers	O
in	O
the	O
Dave	O
chip	O
.	O
</s>
<s>
The	O
output	O
from	O
the	O
selected	O
register	O
is	O
used	O
as	O
the	O
highest	O
8	O
bits	O
of	O
the	O
22-bit	O
address	O
bus	O
,	O
while	O
the	O
lowest	O
14	O
bits	O
come	O
directly	O
from	O
the	O
Z80	B-General_Concept
address	O
bus	O
.	O
</s>
<s>
Effectively	O
,	O
the	O
64	O
KB	O
address	O
space	O
of	O
the	O
Z80	B-General_Concept
processor	O
is	O
divided	O
into	O
four	O
16k	O
sections	O
.	O
</s>
<s>
The	O
lowest	O
two	O
pages	O
(	O
pages	O
0	O
and	O
1	O
)	O
of	O
the	O
4	O
MB	O
address	O
space	O
contain	O
system	O
ROM	B-Device
.	O
</s>
<s>
The	O
next	O
four	O
pages	O
(	O
2	O
to	O
5	O
)	O
are	O
reserved	O
for	O
a	O
ROM	B-Protocol
cartridge	I-Protocol
(	O
max	O
64	O
KB	O
)	O
.	O
</s>
<s>
The	O
top	O
four	O
pages	O
(	O
pages	O
252	O
to	O
255	O
,	O
totaling	O
64	O
KB	O
)	O
are	O
used	O
as	O
video	O
RAM	B-Architecture
,	O
but	O
can	O
be	O
used	O
for	O
storage	O
of	O
program	O
code	O
and	O
data	O
as	O
well	O
.	O
</s>
<s>
On	O
the	O
128k	O
model	O
,	O
the	O
additional	O
64	O
KB	O
of	O
ram	B-Architecture
is	O
mapped	O
on	O
pages	O
248	O
to	O
251	O
.	O
</s>
<s>
The	O
remaining	O
memory	O
space	O
can	O
be	O
used	O
by	O
external	B-Device
devices	I-Device
and	O
memory	O
modules	O
connected	O
to	O
the	O
expansion	O
bus	O
.	O
</s>
<s>
The	O
case	O
is	O
unusual	O
in	O
that	O
it	O
contains	O
both	O
a	O
full-sized	O
keyboard	O
with	O
programmable	O
function	O
keys	O
,	O
and	O
a	O
joystick	B-Device
.	O
</s>
<s>
The	O
low-profile	O
keyboard	O
is	O
constructed	O
with	O
mechanical	O
keycaps	O
on	O
top	O
of	O
a	O
rubber	O
membrane	O
and	O
has	O
a	O
standard	O
layout	O
,	O
but	O
the	O
feel	O
of	O
the	O
keys	O
was	O
disliked	O
by	O
many	O
,	O
or	O
even	O
most	O
people	O
,	O
because	O
the	O
keys	O
were	O
n't	O
"	O
full	O
travel	O
"	O
,	O
but	O
had	O
a	O
squishy	O
feel	O
,	O
similar	O
to	O
a	O
Sinclair	B-Device
QL	I-Device
or	O
Spectrum+	O
.	O
</s>
<s>
The	O
joystick	B-Device
replaces	O
the	O
normal	O
cursor	O
keys	O
,	O
and	O
allows	O
the	O
cursor	O
to	O
be	O
moved	O
diagonally	O
.	O
</s>
<s>
Enterprise	O
has	O
four	O
hardware	O
graphics	O
modes	O
:	O
40-column	O
text	O
modes	O
,	O
Lo-Res	O
and	O
Hi-Res	O
bit	B-Algorithm
mapped	I-Algorithm
graphics	O
,	O
and	O
attribute	O
graphics	O
.	O
</s>
<s>
Bit	B-Algorithm
mapped	I-Algorithm
graphics	O
modes	O
allow	O
selection	O
between	O
displays	O
of	O
2	O
,	O
4	O
,	O
16	O
or	O
256	O
colours	O
(	O
from	O
a	O
3-3-2	O
bit	O
RGB	O
palette	O
)	O
,	O
but	O
horizontal	O
resolution	O
decreases	O
as	O
colour	O
depth	O
increases	O
.	O
</s>
<s>
The	O
maximum	O
resolution	O
is	O
640×512	O
pixels	B-Algorithm
interlaced	O
,	O
or	O
640×256	O
pixels	B-Algorithm
non-interlaced	O
.	O
</s>
<s>
The	O
attribute	O
graphics	O
mode	O
provides	O
a	O
320×256	O
pixel	B-Algorithm
resolution	O
with	O
16	O
colours	O
,	O
selectable	O
from	O
a	O
palette	O
of	O
256	O
.	O
</s>
<s>
Available	O
effects	O
include	O
distortion	O
,	O
low-pass	B-Algorithm
and	O
high-pass	O
filters	O
,	O
and	O
ring	O
modulation	O
.	O
</s>
<s>
There	O
is	O
an	O
RGB	O
output	O
,	O
a	O
RS-232	O
/	O
RS-423	O
serial	O
port	O
,	O
a	O
Centronics	O
printer	O
port	O
,	O
two	O
external	O
joystick	B-Device
ports	O
,	O
two	O
cassette	O
tape	O
interfaces	O
,	O
a	O
ROM	B-Protocol
cartridge	I-Protocol
slot	O
,	O
and	O
an	O
ordinary	O
expansion	O
port	O
.	O
</s>
<s>
The	O
BASIC	O
ROM	B-Device
can	O
be	O
replaced	O
by	O
a	O
ROM	B-Device
that	O
emulates	O
a	O
ZX	B-Operating_System
Spectrum	I-Operating_System
,	O
which	O
allows	O
the	O
Enterprise	O
to	O
run	O
the	O
catalogue	O
of	O
thousands	O
of	O
Spectrum	O
BASIC	O
games	O
and	O
any	O
other	O
titles	O
that	O
do	O
n't	O
access	O
hardware	O
directly	O
;	O
a	O
hardware	O
peripheral	O
was	O
available	O
to	O
provide	O
more	O
complete	O
emulation	O
for	O
other	O
Spectrum	O
titles	O
—	O
catching	O
Spectrum	O
hardware	O
accesses	O
and	O
issuing	O
an	O
interrupt	O
so	O
that	O
emulation	O
software	O
can	O
deal	O
with	O
them	O
.	O
</s>
<s>
An	O
external	O
floppy	B-Device
drive	I-Device
became	O
available	O
later	O
,	O
and	O
allowed	O
access	O
to	O
CP/M	B-Application
programs	O
,	O
while	O
at	O
the	O
same	O
time	O
being	O
compatible	O
with	O
the	O
MS-DOS	B-Application
disc	O
format	O
and	O
FAT12	B-Application
file	O
structure	O
(	O
sub-directories	O
etc	O
.	O
</s>
<s>
EXOS	O
(	O
Enterprise	O
Expandable	O
Operating	O
System	O
)	O
is	O
contained	O
in	O
the	O
system	O
ROM	B-Device
,	O
and	O
is	O
based	O
on	O
"	O
channels	O
"	O
.	O
</s>
<s>
All	O
peripherals	B-Device
are	O
accessed	O
through	O
channels	O
,	O
which	O
allows	O
the	O
programs	O
to	O
treat	O
all	O
input	O
and	O
output	O
devices	O
identically	O
.	O
</s>
<s>
The	O
system	O
ROM	B-Device
also	O
contains	O
a	O
full-screen	O
editor	O
,	O
which	O
doubles	O
as	O
a	O
simple	O
word	O
processor	O
.	O
</s>
<s>
The	O
editor	O
uses	O
the	O
joystick	B-Device
for	O
cursor	O
control	O
.	O
</s>
<s>
Enterprise	O
does	O
not	O
include	O
BASIC	O
or	O
any	O
other	O
programming	O
language	O
in	O
its	O
internal	O
ROM	B-Device
,	O
unlike	O
most	O
other	O
home	O
computers	O
of	O
the	O
time	O
.	O
</s>
<s>
Its	O
BASIC	O
interpreter	O
was	O
supplied	O
on	O
a	O
16k	O
ROM	B-Protocol
cartridge	I-Protocol
,	O
and	O
the	O
language	O
can	O
be	O
changed	O
by	O
switching	O
the	O
cartridge	B-Protocol
,	O
a	O
system	O
similar	O
to	O
that	O
of	O
Acorn	O
's	O
BBC	B-Device
Micro	I-Device
.	O
</s>
<s>
IS-Basic	O
adheres	O
to	O
the	O
ANSI	B-Language
BASIC	I-Language
standard	O
.	O
</s>
<s>
Peripherals	B-Device
can	O
be	O
controlled	O
directly	O
from	O
BASIC	O
,	O
so	O
there	O
is	O
rarely	O
a	O
need	O
to	O
use	O
POKE	O
and	O
PEEK	O
statements	O
.	O
</s>
<s>
IS-Basic	O
has	O
the	O
usual	O
commands	O
for	O
drawing	O
dots	O
,	O
lines	O
,	O
circles	O
and	O
ellipses	O
and	O
for	O
filling	O
areas	O
,	O
and	O
supports	O
Logo-style	O
turtle	B-Application
graphics	I-Application
.	O
</s>
<s>
Several	O
languages	O
besides	O
IS-BASIC	O
,	O
including	O
Forth	O
,	O
Lisp	O
,	O
Pascal	O
and	O
assembly	O
,	O
were	O
available	O
on	O
either	O
ROM	B-Protocol
cartridge	I-Protocol
or	O
tape	O
.	O
</s>
<s>
IS-DOS	O
,	O
the	O
CP/M	B-Application
compatible	O
operating	O
system	O
,	O
opened	O
access	O
to	O
the	O
wide	O
range	O
of	O
CP/M	B-Application
programs	O
available	O
at	O
that	O
time	O
.	O
</s>
<s>
After	O
the	O
1982	O
introduction	O
of	O
the	O
ZX	B-Operating_System
Spectrum	I-Operating_System
,	O
Hong	O
Kong	O
trading	O
company	O
Locumals	O
commissioned	O
Intelligent	O
Software	O
,	O
headed	O
by	O
international	O
chess	B-Application
player	O
David	O
Levy	O
,	O
to	O
develop	O
a	O
home	O
computer	O
in	O
the	O
UK	O
.	O
</s>
<s>
Entersoft	O
,	O
modeled	O
after	O
Amstrad	O
's	O
AMSOFT	B-Device
,	O
was	O
set	O
up	O
to	O
ensure	O
a	O
steady	O
supply	O
of	O
software	O
for	O
the	O
new	O
machine	O
.	O
</s>
<s>
The	O
product	O
did	O
not	O
ship	O
until	O
1985	O
,	O
by	O
which	O
point	O
the	O
UK	O
home	O
computer	O
market	O
was	O
already	O
dominated	O
by	O
the	O
ZX	B-Operating_System
Spectrum	I-Operating_System
,	O
Commodore	O
64	O
,	O
Amstrad	O
CPC	O
and	O
Acorn	B-Device
BBC	I-Device
Micro	I-Device
.	O
</s>
<s>
A	O
successor	O
machine	O
,	O
the	O
PW360	O
,	O
was	O
developed	O
in	O
1986	O
to	O
compete	O
against	O
the	O
Amstrad	B-Device
PCW	I-Device
8256	O
,	O
but	O
the	O
company	O
was	O
by	O
then	O
in	O
severe	O
financial	O
difficulties	O
,	O
and	O
closed	O
down	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
Amstrad	B-Device
CPC	I-Device
464	I-Device
included	O
a	O
monitor	O
and	O
cassette	O
recorder	O
,	O
was	O
released	O
before	O
the	O
Enterprise	O
,	O
and	O
retailed	O
for	O
less	O
.	O
</s>
