<s>
The	O
Epson	B-Device
HX-20	I-Device
(	O
also	O
known	O
as	O
the	O
HC-20	B-Device
)	O
was	O
the	O
first	O
"	O
true	O
"	O
laptop	B-Device
computer	I-Device
.	O
</s>
<s>
It	O
was	O
announced	O
in	O
1981	O
as	O
the	O
HC-20	B-Device
in	O
Japan	O
,	O
and	O
was	O
introduced	O
by	O
Epson	O
in	O
North	O
America	O
as	O
the	O
HX-20	B-Device
at	O
the	O
1981	O
COMDEX	O
computer	O
show	O
in	O
Las	O
Vegas	O
,	O
where	O
it	O
drew	O
significant	O
attention	O
for	O
its	O
portability	O
.	O
</s>
<s>
It	O
had	O
a	O
mass-market	O
release	O
in	O
July	O
1982	O
,	O
as	O
the	O
HC-20	B-Device
in	O
Japan	O
and	O
as	O
the	O
Epson	B-Device
HX-20	I-Device
in	O
North	O
America	O
.	O
</s>
<s>
The	O
size	O
of	O
an	O
A4	O
notebook	B-Device
and	O
weighing	O
1.6kg	O
,	O
it	O
was	O
hailed	O
by	O
BusinessWeek	O
magazine	O
as	O
the	O
"	O
fourth	O
revolution	O
in	O
personal	B-Device
computing	I-Device
"	O
.	O
</s>
<s>
Epson	O
advertised	O
the	O
HX-20	B-Device
with	O
a	O
photograph	O
and	O
photo	O
editing	O
of	O
the	O
computer	O
on	O
two	O
facing	O
magazine	O
pages	O
with	O
the	O
headline	O
"	O
Actual	O
size	O
"	O
.	O
</s>
<s>
With	O
about	O
the	O
footprint	O
of	O
an	O
A4	O
size	O
page	O
,	O
the	O
Epson	B-Device
HX-20	I-Device
features	O
a	O
full-transit	O
keyboard	B-Device
,	O
rechargeable	O
nickel-cadmium	O
batteries	O
,	O
a	O
built-in	O
120	O
×	O
32-pixel	O
LCD	B-Device
which	O
allowed	O
4	O
lines	O
of	O
20	O
characters	O
,	O
a	O
calculator-size	O
dot-matrix	O
printer	O
,	O
the	O
EPSON	O
BASIC	O
programming	O
language	O
,	O
two	O
CPUs	O
at	O
which	O
is	O
essentially	O
an	O
enhanced	O
Motorola	B-Device
6801	I-Device
,	O
RAM	B-Architecture
expandable	O
to	O
,	O
two	O
RS-232	O
ports	O
at	O
a	O
maximum	O
of	O
for	O
the	O
first	O
8-pin	O
DIN	O
connector	O
intended	O
for	O
modem	O
or	O
serial	O
printer	O
with	O
the	O
second	O
port	O
capable	O
of	O
using	O
a	O
5-pin	O
DIN	O
connector	O
which	O
was	O
mainly	O
for	O
use	O
with	O
external	O
floppy	O
drive	O
and	O
video	O
display	O
an	O
early	O
concept	O
of	O
docking	O
station	O
,	O
a	O
acoustic	B-Device
coupler	I-Device
was	O
available	O
,	O
built-in	O
microcassette	O
drive	O
,	O
barcode	O
reader	O
connector	O
.	O
</s>
<s>
Uses	O
a	O
proprietary	O
operating	B-General_Concept
system	I-General_Concept
,	O
which	O
consists	O
of	O
the	O
EPSON	O
BASIC	O
interpreter	B-Application
and	O
a	O
monitor	B-General_Concept
program	O
,	O
and	O
weighs	O
approximately	O
.	O
</s>
<s>
The	O
HX-20	B-Device
was	O
supplied	O
with	O
a	O
grey	O
or	O
brown	O
carry	O
case	O
.	O
</s>
<s>
An	O
external	O
acoustic	B-Device
coupler	I-Device
,	O
the	O
CX-20	O
,	O
was	O
available	O
for	O
the	O
HX-20	B-Device
,	O
as	O
was	O
an	O
external	O
floppy	O
disk	O
drive	O
,	O
the	O
TF-20	O
,	O
and	O
an	O
external	O
speech	O
synthesis	O
Augmentative	O
Communication	O
Device	O
(	O
ACD	O
)	O
,	O
'	O
RealVoice	O
 '	O
.	O
</s>
<s>
The	O
battery	O
life	O
of	O
the	O
HX-20	B-Device
was	O
approximately	O
running	O
BASIC	O
and	O
less	O
using	O
the	O
microcassette	O
,	O
printer	O
or	O
RS-232	O
.	O
</s>
<s>
The	O
HX-20	B-Device
could	O
be	O
stored	O
between	O
.	O
</s>
<s>
The	O
later	O
,	O
more	O
popular	O
TRS-80	B-Operating_System
Model	I-Operating_System
100	I-Operating_System
line	I-Operating_System
,	O
designed	O
by	O
Kyocera	O
,	O
owed	O
much	O
to	O
the	O
design	O
of	O
the	O
HX-20	B-Device
.	O
</s>
<s>
BYTE	B-Application
in	O
September	O
1983	O
wrote	O
that	O
the	O
HX-20	B-Device
,	O
available	O
in	O
the	O
United	O
States	O
for	O
about	O
a	O
year	O
,	O
had	O
been	O
unsuccessful	O
because	O
of	O
the	O
lack	O
of	O
software	O
or	O
accessories	O
.	O
</s>
<s>
BYTE	B-Application
praised	O
the	O
printer	O
as	O
"	O
nothing	O
short	O
of	O
amazing	O
"	O
,	O
but	O
criticized	O
the	O
lack	O
of	O
an	O
operating	B-General_Concept
system	I-General_Concept
for	O
cassette	O
storage	O
and	O
said	O
that	O
compared	O
to	O
the	O
TRS-80	B-Operating_System
Model	I-Operating_System
100	I-Operating_System
's	O
display	O
,	O
"	O
the	O
HX-20	B-Device
looks	O
primitive	O
"	O
.	O
</s>
<s>
The	O
LCD	B-Device
is	O
120×32	O
pixels	O
and	O
is	O
controlled	O
by	O
six	O
μPD7227	O
LCD	B-Device
controller	O
ICs	O
each	O
responsible	O
for	O
40×16	O
pixels	O
of	O
the	O
LCD	B-Device
.	O
</s>
<s>
Each	O
bank	O
is	O
40	O
bytes	B-Application
with	O
bit	O
6	O
of	O
the	O
address	O
determining	O
the	O
bank	O
and	O
even	O
though	O
the	O
address	O
can	O
be	O
up	O
to	O
127	O
,	O
nothing	O
will	O
happen	O
when	O
trying	O
to	O
access	O
data	O
outside	O
the	O
banks	O
.	O
</s>
<s>
The	O
Monitor	B-General_Concept
program	O
can	O
be	O
accessed	O
via	O
the	O
main	O
menu	O
on	O
startup	O
by	O
pressing	O
1	O
,	O
by	O
typing	O
the	O
command	O
"	O
MON	O
"	O
in	O
BASIC	O
or	O
by	O
causing	O
a	O
trap	O
,	O
i.e.	O
</s>
<s>
will	O
be	O
displayed	O
in	O
the	O
Monitor	B-General_Concept
and	O
the	O
user	O
can	O
use	O
it	O
for	O
debugging	O
.	O
</s>
<s>
When	O
entering	O
Monitor	B-General_Concept
it	O
shows	O
a	O
prompt	O
on	O
the	O
first	O
line	O
,	O
"	O
Trap	O
!	O
"	O
</s>
<s>
on	O
the	O
second	O
line	O
(	O
if	O
entered	O
via	O
a	O
trap	O
)	O
and	O
the	O
CPU	B-General_Concept
registers	I-General_Concept
as	O
they	O
were	O
right	O
before	O
the	O
Monitor	B-General_Concept
was	O
entered	O
on	O
the	O
third	O
and	O
fourth	O
lines	O
.	O
</s>
<s>
These	O
registers	B-General_Concept
are	O
A	O
(	O
Accumulator	B-General_Concept
A	O
)	O
,	O
B	O
(	O
Accumulator	B-General_Concept
B	O
)	O
,	O
X	O
(	O
Index	O
Register	O
)	O
,	O
C	O
(	O
Condition	O
Code	O
Register	O
)	O
,	O
S	O
(	O
Stack	O
Pointer	O
)	O
and	O
P	O
(	O
Program	B-General_Concept
Counter	I-General_Concept
)	O
.	O
</s>
<s>
Monitor	B-General_Concept
can	O
be	O
used	O
for	O
reading	O
and	O
writing	O
memory	O
,	O
modifying	O
CPU	B-General_Concept
registers	I-General_Concept
,	O
running	O
code	O
at	O
specific	O
addresses	O
in	O
memory	O
,	O
saving/loading	O
memory	O
to/from	O
a	O
plugin	O
option	O
,	O
etc	O
.	O
</s>
<s>
This	O
is	O
very	O
useful	O
for	O
debugging	O
programs	O
written	O
in	O
machine	B-Language
code	I-Language
in	O
difference	O
to	O
programs	O
written	O
in	O
the	O
EPSON	O
BASIC	O
programming	O
language	O
.	O
</s>
<s>
G	O
(	O
Go	O
)	O
Sets	O
the	O
programme	B-General_Concept
counter	I-General_Concept
to	O
the	O
16-bit	O
address	O
<addr> and will return to Monitor before the breakpoint address <breakpoint>	O
is	O
executed	O
.	O
</s>
<s>
The	O
RETURN	O
key	O
applies	O
the	O
changed	O
value	O
(	O
if	O
any	O
)	O
and	O
jumps	O
between	O
registers	B-General_Concept
.	O
</s>
<s>
B	O
(	O
Back	O
)	O
Return	O
to	O
the	O
procedure	O
from	O
which	O
Monitor	B-General_Concept
was	O
called	O
.	O
</s>
<s>
ROM	O
#0	O
and	O
#1	O
are	O
known	O
as	O
the	O
I/O	O
ROMs	O
,	O
handling	O
system	O
reset	O
and	O
providing	O
functions	O
for	O
using	O
the	O
LCD	B-Device
,	O
keyboard	B-Device
,	O
clock	O
,	O
printer	O
,	O
speaker	O
,	O
serial	O
communication	O
,	O
etc	O
.	O
</s>
<s>
The	O
I/O	O
ROMs	O
are	O
equivalent	O
to	O
the	O
BIOS	O
in	O
modern	O
PCs	B-Device
.	O
</s>
<s>
FFFE-FFFF	O
determines	O
what	O
the	O
program	B-General_Concept
counter	I-General_Concept
should	O
be	O
set	O
to	O
on	O
power	O
up	O
or	O
reset	O
.	O
</s>
<s>
In	O
the	O
standard	O
set	O
of	O
ROMs	O
for	O
the	O
HX-20	B-Device
,	O
this	O
value	O
is	O
E000	O
,	O
the	O
start	O
of	O
ROM	O
#0	O
.	O
</s>
<s>
ROM	O
#2	O
and	O
#3	O
contains	O
the	O
BASIC	O
interpreter	B-Application
.	O
</s>
<s>
If	O
the	O
BASIC	O
ROMs	O
are	O
removed	O
from	O
the	O
motherboard	O
,	O
the	O
BASIC	O
option	O
in	O
the	O
main	O
menu	O
will	O
disappear	O
,	O
leaving	O
only	O
MONITOR	B-General_Concept
.	O
</s>
<s>
The	O
Expansion	O
unit	O
added	O
up	O
to	O
16	O
kByte	O
of	O
RAM	B-Architecture
and	O
two	O
ROM	O
sockets	O
.	O
</s>
