<s>
The	O
Tandy	B-Device
Pocket	I-Device
Computer	I-Device
or	O
TRS-80	B-Device
Pocket	I-Device
Computer	I-Device
is	O
one	O
of	O
a	O
line	O
of	O
1980s	O
small	O
pocket	O
computerscalculator-sized	O
programmable	O
computing	O
devicessold	O
by	O
Tandy	O
Corporation	O
under	O
the	O
"	O
Tandy	O
"	O
or	O
"	O
Radio	B-Device
Shack	I-Device
TRS-80	I-Device
"	O
brands	O
.	O
</s>
<s>
Although	O
named	O
after	O
the	O
TRS-80	B-Device
line	O
of	O
computers	O
,	O
they	O
were	O
not	O
compatible	O
with	O
it	O
and	O
did	O
not	O
use	O
the	O
Z-80	B-General_Concept
CPU	O
.	O
</s>
<s>
Although	O
not	O
branded	O
as	O
such	O
,	O
the	O
original	O
TRS-80	B-Device
Pocket	I-Device
Computer	I-Device
later	O
became	O
known	O
as	O
the	O
PC-1	O
,	O
as	O
subsequent	O
models	O
were	O
labelled	O
PC-2	O
through	O
PC-8	O
.	O
</s>
<s>
The	O
Tandy/TRS	O
-80	O
model	O
names	O
are	O
listed	O
with	O
the	O
corresponding	O
original	O
Sharp	O
or	O
Casio	O
model	O
number	O
.	O
</s>
<s>
Pocket	B-Device
computers	I-Device
were	O
an	O
advancement	O
over	O
early	O
programmable	B-Application
calculator	I-Application
designs	O
.	O
</s>
<s>
In	O
addition	O
to	O
providing	O
users	O
with	O
scientific	O
math	O
functions	O
in	O
a	O
small	O
portable	O
package	O
,	O
the	O
devices	O
also	O
understood	O
a	O
form	O
of	O
the	O
BASIC	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
They	O
included	O
a	O
QWERTY	O
keyboard	B-Device
,	O
of	O
either	O
rubber	B-Device
capacitive	I-Device
or	O
membrane	B-Device
type	I-Device
,	O
to	O
use	O
for	O
entering	O
the	O
names	O
of	O
scientific	O
functions	O
and	O
programming	O
commands	O
,	O
in	O
addition	O
to	O
a	O
traditional	O
numeric	B-Device
keypad	I-Device
.	O
</s>
<s>
(	O
The	O
exception	O
was	O
the	O
PC-7	O
,	O
which	O
had	O
a	O
rectangular	O
and	O
alphabetically	O
ordered	O
keyboard	B-Device
,	O
like	O
most	O
scientific	O
calculators	O
.	O
)	O
</s>
<s>
On	O
some	O
models	O
,	O
the	O
alphanumeric	O
keypad	O
had	O
a	O
different	O
type	O
,	O
form	O
factor	O
,	O
and	O
location	O
than	O
the	O
numeric	B-Device
keypad	I-Device
.	O
</s>
<s>
The	O
models	O
provided	O
a	O
short	O
one-line	O
dot-matrix	B-General_Concept
LCD	B-Device
display	I-Device
,	O
to	O
show	O
the	O
current	O
line	O
of	O
input	O
text	O
,	O
or	O
a	O
segment	O
of	O
it	O
containing	O
the	O
cursor	B-Application
.	O
</s>
<s>
In	O
Run	O
mode	O
,	O
the	O
command	B-Application
line	I-Application
could	O
be	O
openly	O
used	O
to	O
execute	O
one-line	O
,	O
non-BASIC	O
operations	O
.	O
</s>
<s>
The	O
Run	O
mode	O
also	O
allowed	O
the	O
execution	B-General_Concept
of	O
the	O
BASIC	O
programs	O
stored	O
in	O
the	O
device	O
.	O
</s>
<s>
The	O
input	O
of	O
simple	O
calculations	O
would	O
be	O
aggregated	O
on	O
the	O
command	B-Application
line	I-Application
,	O
and	O
no	O
results	O
would	O
be	O
displayed	O
until	O
the	O
EXE	O
key	O
was	O
pressed	O
.	O
</s>
<s>
The	O
Prog	O
mode	O
changed	O
the	O
input	O
from	O
a	O
command	B-Application
line	I-Application
to	O
a	O
program	O
editor	O
.	O
</s>
<s>
On	O
the	O
Sharp	O
models	O
,	O
there	O
was	O
only	O
one	O
line	B-Application
numbering	I-Application
space	O
.	O
</s>
<s>
In	O
order	O
for	O
multiple	O
programs	O
to	O
exist	O
on	O
the	O
device	O
,	O
they	O
had	O
to	O
be	O
written	O
in	O
different	O
ranges	O
of	O
line	B-Application
numbers	I-Application
.	O
</s>
<s>
Valid	O
line	B-Application
numbers	I-Application
in	O
most	O
models	O
were	O
from	O
1	O
to	O
999	O
.	O
</s>
<s>
To	O
prevent	O
run-on	O
execution	B-General_Concept
,	O
each	O
program	O
had	O
to	O
finish	O
with	O
the	O
END	O
command	O
,	O
unless	O
run-on	O
execution	B-General_Concept
was	O
desired	O
.	O
</s>
<s>
This	O
was	O
equivalent	O
to	O
an	O
explicit	O
GOTO	B-Application
command	O
to	O
the	O
first	O
line	B-Application
number	I-Application
of	O
that	O
section	O
of	O
program	O
,	O
which	O
was	O
also	O
a	O
valid	O
way	O
to	O
execute	O
programs	O
from	O
Run	O
mode	O
.	O
</s>
<s>
Many	O
of	O
the	O
devices	O
included	O
a	O
special	O
modifier	B-Device
key	I-Device
to	O
expedite	O
the	O
entry	O
of	O
BASIC	O
commands	O
as	O
well	O
as	O
scientific	O
function	O
names	O
.	O
</s>
<s>
The	O
most	O
common	O
commands	O
would	O
each	O
be	O
associated	O
with	O
a	O
key	O
,	O
and	O
the	O
full	O
command	O
could	O
be	O
entered	O
by	O
depressing	O
the	O
special	O
modifier	B-Device
key	I-Device
,	O
followed	O
by	O
the	O
associated	O
key	O
for	O
the	O
command	O
.	O
</s>
<s>
The	O
total	O
memory	O
capacity	O
of	O
the	O
devices	O
varied	O
from	O
1KB	O
to	O
12KB	O
and	O
up	O
as	O
far	O
as	O
16KB	O
with	O
the	O
use	O
of	O
an	O
available	O
RAM	B-Architecture
card	O
(	O
only	O
for	O
some	O
models	O
)	O
.	O
</s>
<s>
The	O
optional	O
RAM	B-Architecture
cards	O
varied	O
in	O
sizes	O
from	O
1KB	O
,	O
4KB	O
and	O
8KB	O
.	O
</s>
<s>
Errors	O
encountered	O
either	O
in	O
program	O
execution	B-General_Concept
or	O
calculation	O
evaluation	O
would	O
be	O
returned	O
as	O
one	O
of	O
9	O
error	O
codes	O
,	O
usually	O
indicated	O
by	O
replacing	O
the	O
display	O
with	O
text	O
such	O
as	O
"	O
ERROR	O
4	O
"	O
.	O
</s>
<s>
and	O
-	O
the	O
highest	O
memory	O
location	O
is	O
2047	O
,	O
and	O
it	O
is	O
possible	O
to	O
modify	O
the	O
BASIC	O
program	O
in	O
RAM	B-Architecture
directly	O
with	O
,	O
as	O
well	O
as	O
access	O
a	O
certain	O
memory	O
location	O
(	O
37	O
,	O
possibly	O
?	O
)	O
</s>
<s>
that	O
controls	O
the	O
DEG/RAD/GRAD	O
spots	O
on	O
the	O
LCD	B-Device
.	O
</s>
<s>
Will	O
show	O
a	O
couple	O
of	O
patterns	O
on	O
the	O
LCD	B-Device
and	O
then	O
appear	O
to	O
lock	O
up	O
.	O
</s>
