<s>
The	O
VT50	B-Application
was	O
a	O
CRT-based	O
computer	B-General_Concept
terminal	I-General_Concept
introduced	O
by	O
Digital	O
Equipment	O
Corporation	O
(	O
DEC	O
)	O
in	O
July	O
1974	O
.	O
</s>
<s>
It	O
provided	O
a	O
display	O
with	O
12	O
rows	O
and	O
80	O
columns	O
of	O
upper-case	O
text	O
,	O
and	O
used	O
an	O
expanded	O
set	O
of	O
control	O
characters	O
and	O
forward-only	O
scrolling	O
based	O
on	O
the	O
earlier	O
VT05	B-Application
.	O
</s>
<s>
DEC	O
documentation	O
of	O
the	O
era	O
refers	O
to	O
the	O
terminals	O
as	O
the	O
DECscope	B-Application
,	O
a	O
name	O
that	O
was	O
otherwise	O
almost	O
never	O
seen	O
.	O
</s>
<s>
The	O
VT50	B-Application
was	O
sold	O
only	O
for	O
a	O
short	O
period	O
before	O
it	O
was	O
replaced	O
by	O
the	O
VT52	B-Application
in	O
September	O
1975	O
.	O
</s>
<s>
The	O
VT52	B-Application
provided	O
a	O
screen	O
of	O
24	O
rows	O
and	O
80	O
columns	O
of	O
text	O
and	O
supported	O
all	O
95	O
ASCII	B-Protocol
characters	I-Protocol
as	O
well	O
as	O
32	O
graphics	O
characters	O
,	O
bi-directional	O
scrolling	O
,	O
and	O
an	O
expanded	O
control	O
character	O
system	O
.	O
</s>
<s>
DEC	O
produced	O
a	O
series	O
of	O
upgraded	O
VT52	B-Application
's	O
with	O
additional	O
hardware	O
for	O
various	O
uses	O
.	O
</s>
<s>
The	O
VT52	B-Application
family	O
was	O
followed	O
by	O
the	O
much	O
more	O
sophisticated	O
VT100	B-Device
in	O
1978	O
.	O
</s>
<s>
The	O
VT50	B-Application
supported	O
asynchronous	O
communication	O
at	O
baud	O
rates	O
up	O
to	O
9600	O
bits	O
per	O
second	O
and	O
did	O
not	O
require	O
any	O
fill	B-General_Concept
characters	I-General_Concept
.	O
</s>
<s>
Like	O
other	O
early	O
DEC	O
terminals	O
,	O
the	O
VT50	B-Application
series	O
were	O
equipped	O
with	O
both	O
an	O
RS-232	O
port	O
as	O
well	O
as	O
a	O
20mA	O
current	O
loop	O
,	O
an	O
older	O
serial	O
standard	O
used	O
with	O
teletype	O
machines	O
that	O
was	O
more	O
suitable	O
for	O
transmission	O
over	O
long	O
runs	O
of	O
twisted-pair	O
wiring	O
.	O
</s>
<s>
To	O
interpret	O
the	O
commands	O
being	O
sent	O
in	O
the	O
serial	O
data	O
,	O
it	O
used	O
a	O
primitive	O
central	B-General_Concept
processing	I-General_Concept
unit	I-General_Concept
(	O
CPU	O
)	O
built	O
from	O
small-scale-integration	O
integrated	O
circuits	O
.	O
</s>
<s>
One	O
notable	O
feature	O
of	O
the	O
VT50	B-Application
was	O
the	O
introduction	O
of	O
a	O
separate	O
function	O
keypad	O
with	O
the	O
"	O
Gold	B-Device
Key	I-Device
"	O
,	O
which	O
was	O
used	O
for	O
editing	O
programs	O
like	O
WPS-8	B-Protocol
,	O
KED	O
,	O
and	O
EDT	B-Application
.	O
</s>
<s>
Pressing	O
the	O
Gold	B-Device
Key	I-Device
and	O
then	O
typing	O
one	O
of	O
the	O
keys	O
on	O
the	O
keyboard	O
sent	O
a	O
command	O
sequence	O
back	O
to	O
the	O
host	O
computer	O
.	O
</s>
<s>
The	O
VT50	B-Application
was	O
the	O
first	O
terminal	O
Digital	O
produced	O
in	O
this	O
cabinet	O
.	O
</s>
<s>
Like	O
its	O
predecessor	O
,	O
the	O
VT05	B-Application
,	O
the	O
VT50	B-Application
did	O
not	O
support	O
lowercase	O
letters	O
.	O
</s>
<s>
The	O
VT50	B-Application
was	O
soon	O
replaced	O
by	O
the	O
greatly	O
upgraded	O
VT52	B-Application
.	O
</s>
<s>
The	O
VT52	B-Application
had	O
considerably	O
larger	O
buffers	O
,	O
giving	O
it	O
the	O
capacity	O
to	O
store	O
not	O
only	O
a	O
full	O
24	O
lines	O
of	O
text	O
that	O
better	O
utilized	O
the	O
screen	O
space	O
,	O
but	O
also	O
the	O
text	O
off	O
the	O
top	O
and	O
bottom	O
of	O
the	O
screen	O
.	O
</s>
<s>
The	O
VT52	B-Application
also	O
included	O
lowercase	O
text	O
support	O
and	O
a	O
host	O
of	O
other	O
new	O
features	O
.	O
</s>
<s>
It	O
was	O
the	O
first	O
DEC	O
terminal	O
that	O
allowed	O
WYSIWYG	B-Application
(	O
"	O
What	B-Application
you	I-Application
see	I-Application
is	I-Application
what	I-Application
you	I-Application
get	I-Application
"	O
)	O
text	O
editing	O
.	O
</s>
<s>
The	O
VT55	O
incorporated	O
an	O
add-on	O
graphics	O
system	O
that	O
was	O
capable	O
of	O
displaying	O
two	O
mathematical	O
functions	O
or	O
histograms	B-Algorithm
.	O
</s>
<s>
Both	O
systems	O
mixed	O
their	O
data	O
during	O
the	O
display	O
,	O
allowing	O
the	O
user	O
to	O
mix	O
graphics	O
and	O
text	O
on	O
a	O
single	O
screen	O
,	O
as	O
opposed	O
to	O
systems	O
like	O
the	O
Tektronix	B-General_Concept
4010	I-General_Concept
or	O
plotters	B-Operating_System
that	O
had	O
to	O
slowly	O
draw	O
text	O
using	O
graphics	O
commands	O
.	O
</s>
<s>
The	O
VT61	B-Application
and	O
VT62	O
were	O
block-mode	O
terminals	O
.	O
</s>
<s>
The	O
VT62	O
was	O
to	O
be	O
used	O
in	O
conjunction	O
with	O
TRAX	O
,	O
a	O
transaction	O
processing	O
operating	O
system	O
on	O
high-end	O
PDP-11	B-Device
'	O
s	O
.	O
</s>
<s>
Application-specific	O
behavior	O
was	O
coded	O
in	O
separate	O
PROM	B-General_Concept
memory	O
,	O
using	O
a	O
separate	O
instruction	O
code	O
that	O
the	O
processor	O
interpreted	O
.	O
</s>
<s>
The	O
relatively	O
large	O
expansion	O
area	O
of	O
the	O
VT50	B-Application
case	O
,	O
combined	O
with	O
rapidly	O
shrinking	O
electronics	O
in	O
the	O
late	O
1970s	O
,	O
allowed	O
DEC	O
to	O
produce	O
single-box	O
,	O
stand-alone	O
minicomputer/terminals	O
similar	O
to	O
a	O
contemporary	O
microcomputer	B-Architecture
.	O
</s>
<s>
The	O
VT78	B-Device
added	O
a	O
single-chip	O
PDP-8	B-Device
processor	O
to	O
the	O
VT52	B-Application
,	O
on	O
which	O
was	O
programmed	O
WPS-8	B-Protocol
,	O
Digital	O
's	O
word	B-General_Concept
processing	I-General_Concept
system	O
.	O
</s>
<s>
VT52	B-Application
codes	O
remained	O
proprietary	O
to	O
DEC	O
,	O
although	O
a	O
number	O
of	O
other	O
companies	O
provided	O
emulations	O
in	O
their	O
terminals	O
.	O
</s>
<s>
One	O
interesting	O
case	O
is	O
the	O
GEMDOS	B-Operating_System
system	O
and	O
its	O
offshoot	O
,	O
the	O
TOS	O
operating	O
system	O
of	O
the	O
Atari	B-Device
ST	I-Device
.	O
</s>
<s>
These	O
systems	O
used	O
a	O
VT52-based	O
screen	O
driver	O
in	O
an	O
era	O
when	O
ANSI	O
escape	O
codes	O
had	O
already	O
become	O
almost	O
universal	O
.	O
</s>
<s>
VT52	B-Application
commands	O
normally	O
consisted	O
of	O
the	O
escape	O
character	O
and	O
a	O
single	O
character	O
following	O
it	O
.	O
</s>
<s>
These	O
numbers	O
were	O
sent	O
as	O
ASCII	B-Protocol
characters	I-Protocol
of	O
that	O
value	O
,	O
adding	O
31	O
.	O
</s>
<s>
For	O
instance	O
,	O
to	O
position	O
the	O
cursor	O
at	O
column	O
30	O
and	O
line	O
20	O
,	O
you	O
would	O
add	O
31	O
to	O
each	O
value	O
to	O
get	O
61	O
and	O
51	O
,	O
then	O
look	O
up	O
those	O
ASCII	B-Protocol
characters	I-Protocol
,	O
and	O
.	O
</s>
<s>
Enter	O
graphics	O
mode	O
Use	O
special	O
graphics	O
character	O
set	O
,	O
VT52	B-Application
and	O
later	O
.	O
</s>
<s>
Set	O
cursor	O
position	O
Move	O
cursor	O
to	O
position	O
c	O
,	O
r	O
,	O
encoded	O
as	O
single	O
characters.The	O
VT50H	O
also	O
added	O
the	O
"	O
SO	O
"	O
command	O
that	O
worked	O
identically	O
,	O
providing	O
backward	O
compatibility	O
with	O
the	O
VT05	B-Application
.	O
</s>
<s>
The	O
VT52	B-Application
and	O
VT55	O
included	O
two	O
characters	O
sets	O
,	O
ASCII	B-Protocol
and	O
"	O
graphics	O
mode	O
"	O
which	O
switched	O
out	O
the	O
lower	O
case	O
characters	O
and	O
some	O
punctuation	O
with	O
new	O
characters	O
useful	O
for	O
the	O
display	O
of	O
math	O
.	O
</s>
<s>
Later	O
VT	O
terminals	O
supported	O
VT52	B-Application
commands	O
,	O
as	O
well	O
as	O
adding	O
a	O
single	O
new	O
command	O
to	O
return	O
to	O
full	O
ANSI	O
mode	O
.	O
</s>
<s>
The	O
GEMDOS	B-Operating_System
version	O
of	O
the	O
VT52	B-Application
command	O
set	O
adds	O
a	O
number	O
of	O
new	O
commands	O
.	O
</s>
<s>
The	O
Atari	B-Device
ST	I-Device
only	O
supported	O
4	O
of	O
those	O
in	O
80	O
column	O
mode	O
and	O
all	O
16	O
in	O
40	O
column	O
mode	O
.	O
</s>
<s>
A	O
few	O
new	O
cursor	O
commands	O
were	O
added	O
as	O
well	O
,	O
essentially	O
filling	O
out	O
the	O
set	O
of	O
the	O
original	O
VT52	B-Application
by	O
including	O
commands	O
that	O
cleared	O
toward	O
the	O
top	O
of	O
the	O
screen	O
instead	O
of	O
the	O
bottom	O
.	O
</s>
<s>
The	O
system	O
did	O
not	O
support	O
a	O
number	O
of	O
VT52	B-Application
commands	O
,	O
including	O
F	O
,	O
G	O
and	O
Z	O
.	O
</s>
