<s>
TECO	B-Application
(	O
)	O
,	O
short	O
for	O
Text	B-Application
Editor	I-Application
&	I-Application
Corrector	I-Application
,	O
is	O
both	O
a	O
character-oriented	O
text	B-Application
editor	I-Application
and	O
a	O
programming	O
language	O
,	O
that	O
was	O
developed	O
in	O
1962	O
for	O
use	O
on	O
Digital	O
Equipment	O
Corporation	O
computers	O
,	O
and	O
has	O
since	O
become	O
available	O
on	O
PCs	B-Device
and	O
Unix	B-Application
.	O
</s>
<s>
Dan	O
Murphy	O
developed	O
TECO	B-Application
while	O
a	O
student	O
at	O
the	O
Massachusetts	O
Institute	O
of	O
Technology	O
(	O
MIT	O
)	O
.	O
</s>
<s>
According	O
to	O
Murphy	O
,	O
the	O
initial	O
acronym	O
was	O
Tape	B-Application
Editor	I-Application
and	I-Application
Corrector	I-Application
because	O
"	O
punched	O
paper	O
tape	O
was	O
the	O
only	O
medium	O
for	O
the	O
storage	O
of	O
program	O
source	O
on	O
our	O
PDP-1	B-Device
.	O
</s>
<s>
It	O
was	O
subsequently	O
modified	O
by	O
many	O
other	O
people	O
and	O
is	O
a	O
direct	O
ancestor	O
of	O
Emacs	B-Application
,	O
which	O
was	O
originally	O
implemented	O
in	O
TECO	B-Application
macros	O
.	O
</s>
<s>
TECO	B-Application
is	O
not	O
only	O
an	O
editor	O
but	O
also	O
an	O
interpreted	B-Application
programming	I-Application
language	I-Application
for	O
text	O
manipulation	O
.	O
</s>
<s>
Unlike	O
regular	B-Language
expressions	I-Language
,	O
however	O
,	O
the	O
language	O
was	O
imperative	B-Application
,	O
though	O
some	O
versions	O
had	O
an	O
"	O
or	O
"	O
operator	O
in	O
string	O
search	O
.	O
</s>
<s>
TECO	B-Application
does	O
not	O
really	O
have	O
syntax	B-Application
;	O
each	O
character	O
in	O
a	O
program	O
is	O
an	O
imperative	B-Application
command	O
,	O
dispatched	O
to	O
its	B-Application
corresponding	O
routine	O
.	O
</s>
<s>
But	O
there	O
is	O
nothing	O
to	O
prevent	O
operations	O
like	O
jumping	O
into	O
the	O
middle	O
of	O
a	O
comment	O
,	O
since	O
there	O
is	O
no	O
syntax	B-Application
and	O
no	O
parsing	O
.	O
</s>
<s>
TECO	B-Application
ignores	O
case	O
and	O
whitespace	O
(	O
except	O
tab	O
,	O
which	O
is	O
an	O
insertion	O
command	O
)	O
.	O
</s>
<s>
A	O
satirical	O
essay	O
on	O
computer	O
programming	O
,	O
Real	O
Programmers	O
Do	O
n't	O
Use	O
Pascal	O
,	O
suggested	O
that	O
a	O
common	O
game	O
for	O
TECO	B-Application
fans	O
was	O
to	O
enter	O
their	O
name	O
as	O
a	O
command	O
sequence	O
,	O
and	O
then	O
try	O
to	O
work	O
out	O
what	O
would	O
happen	O
.	O
</s>
<s>
The	O
same	O
essay	O
in	O
describing	O
TECO	B-Application
coined	O
the	O
acronym	O
YAFIYGI	O
,	O
meaning	O
"	O
You	O
Asked	O
For	O
It	O
You	O
Got	O
It	O
"	O
(	O
in	O
contrast	O
to	O
WYSIWYG	B-Application
)	O
.	O
</s>
<s>
The	O
EMACS	B-Application
editor	O
originally	O
started	O
by	O
David	O
A	O
.	O
</s>
<s>
Moon	O
and	O
Guy	O
L	O
.	O
Steele	O
Jr.	O
was	O
implemented	O
in	O
TECO	B-Application
as	O
a	O
set	O
of	O
Editor	B-Application
MACroS	I-Application
.	O
</s>
<s>
TECO	B-Application
became	O
more	O
widely	O
used	O
following	O
a	O
Digital	O
Equipment	O
Corporation	O
(	O
DEC	O
)	O
PDP-6	B-Device
implementation	O
developed	O
at	O
MIT	O
's	O
Project	O
MAC	O
in	O
1964	O
.	O
</s>
<s>
This	O
implementation	O
continuously	O
displayed	O
the	O
edited	O
text	O
visually	O
on	O
a	O
CRT	B-Device
screen	I-Device
,	O
and	O
was	O
used	O
as	O
an	O
interactive	O
online	O
editor	O
.	O
</s>
<s>
Later	O
versions	O
of	O
TECO	B-Application
were	O
capable	O
of	O
driving	O
full-screen	O
mode	O
on	O
various	O
DEC	O
RS-232	O
video	O
terminals	O
such	O
as	O
the	O
VT52	B-Application
or	O
VT100	B-Device
.	O
</s>
<s>
TECO	B-Application
was	O
available	O
for	O
several	O
operating	O
systems	O
and	O
computers	O
,	O
including	O
the	O
PDP-1	B-Device
computer	O
,	O
the	O
PDP-8	B-Device
(	O
under	O
OS/8	B-Operating_System
)	O
,	O
the	O
Incompatible	B-Application
Timesharing	I-Application
System	I-Application
(	O
ITS	B-Application
)	O
on	O
the	O
PDP-6	B-Device
and	O
PDP-10	B-Device
,	O
and	O
TOPS-10	B-Operating_System
and	O
TOPS-20	B-Operating_System
on	O
the	O
PDP-10	B-Device
.	O
</s>
<s>
A	O
version	O
of	O
TECO	B-Application
was	O
provided	O
with	O
all	O
DEC	O
operating	O
systems	O
;	O
the	O
version	O
available	O
for	O
RT11	B-Operating_System
was	O
able	O
to	O
drive	O
the	O
GT40	O
graphics	O
display	O
while	O
the	O
version	O
available	O
for	O
RSTS/E	B-Operating_System
was	O
implemented	O
as	O
a	O
multi-user	O
run-time	B-Device
system	I-Device
and	O
could	O
be	O
used	O
as	O
the	O
user	O
's	O
complete	O
operating	O
environment	O
;	O
the	O
user	O
never	O
actually	O
had	O
to	O
exit	O
TECO	B-Application
.	O
</s>
<s>
The	O
VTEDIT	O
(	O
Video	O
Terminal	O
Editor	O
)	O
TECO	B-Application
macro	O
was	O
commonly	O
used	O
on	O
RSTS/E	B-Operating_System
and	O
VAX	B-Device
systems	O
with	O
terminals	O
capable	O
of	O
direct-cursor	O
control	O
(	O
e.g.	O
</s>
<s>
VT52	B-Application
and	O
VT100	B-Device
)	O
to	O
provide	O
a	O
full-screen	O
visual	O
editor	O
similar	O
in	O
function	O
to	O
the	O
contemporaneously	O
developed	O
Emacs	B-Application
.	O
</s>
<s>
TECO	B-Application
continues	O
to	O
be	O
included	O
in	O
OpenVMS	B-Operating_System
by	O
VSI	O
,	O
and	O
is	O
invoked	O
with	O
the	O
EDIT/TECO	O
command	O
.	O
</s>
<s>
A	O
descendant	O
of	O
the	O
version	O
DEC	O
distributed	O
for	O
the	O
PDP-10	B-Device
is	O
still	O
available	O
on	O
the	O
Internet	O
,	O
along	O
with	O
several	O
partial	O
implementations	O
for	O
the	O
MS-DOS/Microsoft	O
Windows	O
environment	O
.	O
</s>
<s>
TECO	B-Application
was	O
originally	O
developed	O
at	O
MIT	O
in	O
around	O
1963	O
by	O
Daniel	O
L	O
.	O
Murphy	O
for	O
use	O
on	O
two	O
PDP-1	B-Device
computers	O
,	O
belonging	O
to	O
different	O
departments	O
,	O
both	O
housed	O
in	O
MIT	O
's	O
Building	O
26	O
.	O
</s>
<s>
On	O
these	O
machines	O
,	O
the	O
normal	O
development	O
process	O
involved	O
the	O
use	O
of	O
a	O
Friden	B-Application
Flexowriter	I-Application
to	O
prepare	O
source	O
code	O
offline	O
on	O
a	O
continuous	O
strip	O
of	O
punched	O
paper	O
tape	O
.	O
</s>
<s>
Programmers	O
of	O
the	O
big	O
IBM	B-Device
mainframes	I-Device
customarily	O
punched	O
their	O
source	O
code	O
on	O
cards	O
,	O
using	O
key	B-Device
punches	I-Device
which	O
printed	O
human-readable	O
dot-matrix	B-General_Concept
characters	O
along	O
the	O
top	O
of	O
every	O
card	B-Architecture
at	O
the	O
same	O
time	O
as	O
they	O
punched	O
each	O
machine-readable	O
character	O
.	O
</s>
<s>
An	O
early	O
editor	O
for	O
the	O
PDP-1	B-Device
was	O
named	O
"	O
Expensive	B-Application
Typewriter	I-Application
"	O
.	O
</s>
<s>
Its	B-Application
name	O
was	O
chosen	O
as	O
a	O
wry	O
poke	O
at	O
an	O
earlier	O
,	O
rather	O
bloated	O
,	O
editor	O
called	O
"	O
Colossal	B-Application
Typewriter	I-Application
"	O
.	O
</s>
<s>
Another	O
program	O
written	O
by	O
the	O
PDP-1	B-Device
hackers	O
was	O
Expensive	O
Desk	O
Calculator	O
,	O
in	O
a	O
similar	O
vein	O
.	O
</s>
<s>
The	O
original	O
stated	O
purpose	O
of	O
TECO	B-Application
was	O
to	O
make	O
more	O
efficient	O
use	O
of	O
the	O
PDP-1	B-Device
.	O
</s>
<s>
As	O
envisioned	O
in	O
the	O
manual	O
,	O
rather	O
than	O
performing	O
editing	O
"	O
expensively	O
"	O
by	O
sitting	O
at	O
a	O
console	B-Device
,	O
one	O
would	O
simply	O
examine	O
the	O
faulty	O
text	O
and	O
prepare	O
a	O
"	O
correction	O
tape	O
"	O
describing	O
the	O
editing	O
operations	O
to	O
be	O
performed	O
on	O
the	O
text	O
.	O
</s>
<s>
One	O
would	O
efficiently	O
feed	O
the	O
source	O
tape	O
and	O
the	O
correction	O
tape	O
into	O
the	O
PDP-1	B-Device
via	O
its	B-Application
high-speed	O
(	O
200	O
characters	O
per	O
second	O
)	O
reader	O
.	O
</s>
<s>
Running	O
TECO	B-Application
,	O
it	O
immediately	O
would	O
punch	O
an	O
edited	O
tape	O
with	O
its	B-Application
high-speed	O
(	O
60	O
characters	O
per	O
second	O
)	O
punch	O
.	O
</s>
<s>
TECO	B-Application
's	O
sophisticated	O
searching	O
operations	O
were	O
motivated	O
by	O
the	O
fact	O
that	O
the	O
offline	O
Flexowriter	B-Application
printouts	O
were	O
not	O
line-numbered	O
.	O
</s>
<s>
The	O
various	O
looping	O
and	O
conditional	O
constructs	O
(	O
which	O
made	O
TECO	B-Application
Turing-complete	O
)	O
were	O
included	O
in	O
order	O
to	O
provide	O
sufficient	O
descriptive	O
power	O
for	O
the	O
correction	O
tape	O
.	O
</s>
<s>
The	O
terse	O
syntax	B-Application
minimized	O
the	O
number	O
of	O
keystrokes	O
needed	O
to	O
prepare	O
the	O
correction	O
tape	O
.	O
</s>
<s>
In	O
practice	O
,	O
TECO	B-Application
editing	O
was	O
performed	O
online	O
just	O
as	O
it	O
had	O
been	O
with	O
Expensive	B-Application
Typewriter	I-Application
(	O
although	O
TECO	B-Application
was	O
certainly	O
a	O
more	O
feature-complete	O
editor	O
than	O
Expensive	B-Application
Typewriter	I-Application
,	O
so	O
editing	O
was	O
much	O
more	O
efficient	O
with	O
TECO	B-Application
)	O
.	O
</s>
<s>
The	O
original	O
PDP-1	B-Device
version	O
had	O
no	O
screen	O
display	O
.	O
</s>
<s>
The	O
only	O
way	O
to	O
observe	O
the	O
state	O
of	O
the	O
text	O
during	O
the	O
editing	O
process	O
was	O
to	O
type	O
in	O
commands	O
that	O
would	O
cause	O
the	O
text	O
(	O
or	O
portions	O
thereof	O
)	O
to	O
be	O
typed	O
out	O
on	O
the	O
console	B-Device
typewriter	O
.	O
</s>
<s>
By	O
1964	O
,	O
a	O
special	O
Version	O
of	O
TECO	B-Application
(	O
TECO-6	O
)	O
had	O
been	O
implemented	O
on	O
the	O
PDP-6	B-Device
at	O
MIT	O
.	O
</s>
<s>
Amongst	O
the	O
creators	O
of	O
TECO-6	O
were	O
Richard	O
Greenblatt	O
and	O
Stewart	O
Nelson	O
.	O
</s>
<s>
At	O
MIT	O
,	O
TECO	B-Application
development	O
continued	O
in	O
the	O
fall	O
of	O
1971	O
.	O
</s>
<s>
Carl	O
Mikkelsen	O
had	O
implemented	O
a	O
real-time	O
edit	O
mode	O
loosely	O
based	O
on	O
the	O
TECO-6	O
graphic	O
console	B-Device
commands	O
,	O
but	O
working	O
with	O
the	O
newly	O
installed	O
Datapoint-3300	O
CRT	B-Device
text	O
displays	O
.	O
</s>
<s>
The	O
TECO	B-Application
buffer	O
implementation	O
,	O
however	O
,	O
was	O
terribly	O
inefficient	O
for	O
processing	O
single	O
character	O
insert	O
or	O
delete	O
functions	O
—	O
editing	O
consumed	O
100%	O
of	O
the	O
PDP-10	B-Device
.	O
</s>
<s>
With	O
Richard	O
Greenblatt	O
's	O
support	O
,	O
in	O
summer	O
of	O
1972	O
Carl	O
reimplemented	O
the	O
TECO	B-Application
buffer	O
storage	O
and	O
reformed	O
the	O
macros	O
as	O
native	O
PDP-10	B-Device
code	O
.	O
</s>
<s>
Read-time	O
macros	O
made	O
the	O
TECO	B-Application
auxiliary	O
text	O
buffers	O
,	O
called	O
Q-registers	O
,	O
more	O
useful	O
.	O
</s>
<s>
These	O
edit	O
macros	O
evolved	O
into	O
Emacs	B-Application
.	O
</s>
<s>
The	O
VMS	B-Operating_System
implementation	O
has	O
a	O
long	O
history	O
-	O
it	O
began	O
as	O
TECO-8	O
,	O
implemented	O
in	O
PDP-8	B-Device
assembly	O
.	O
</s>
<s>
This	O
code	O
was	O
translated	O
into	O
PDP-11	O
assembly	O
to	O
produce	O
TECO-11	O
.	O
</s>
<s>
TECO-11	O
was	O
used	O
in	O
early	O
versions	O
of	O
VAX/VMS	B-Operating_System
in	O
PDP-11	O
compatibility	O
mode	O
.	O
</s>
<s>
It	O
was	O
later	O
translated	O
from	O
PDP-11	O
assembly	O
into	O
VAX	B-Device
assembly	O
to	O
produce	O
TECO32	O
.	O
</s>
<s>
TECO32	O
was	O
then	O
converted	O
with	O
the	O
VEST	O
and	O
AEST	O
binary	O
translation	O
utilities	O
to	O
make	O
it	O
compatible	O
with	O
OpenVMS	B-Operating_System
on	O
the	O
Alpha	B-Language
and	O
Itanium	B-General_Concept
respectively	O
.	O
</s>
<s>
The	O
OS/8	B-Operating_System
CCL	B-Operating_System
MUNG	O
command	O
invoked	O
TECO	B-Application
to	O
read	O
and	O
execute	O
the	O
specified	O
.TE	O
TECO	B-Application
macro	O
.	O
</s>
<s>
During	O
and	O
shortly	O
following	O
the	O
years	O
of	O
the	O
punched	B-Architecture
card	I-Architecture
era	O
,	O
there	O
were	O
source	O
programs	O
that	O
had	O
begun	O
as	O
punched	O
card-based	O
.	O
</s>
<s>
TECO	B-Application
to	O
the	O
rescue	O
...	O
</s>
<s>
The	O
obscurity	O
of	O
the	O
TECO	B-Application
programming	I-Application
language	I-Application
is	O
described	O
in	O
the	O
following	O
quote	O
from	O
"	O
Real	O
Programmers	O
Do	O
n't	O
Use	O
Pascal	O
"	O
,	O
a	O
letter	O
from	O
Ed	O
Post	O
to	O
Datamation	O
,	O
July	O
1983	O
:	O
</s>
<s>
According	O
to	O
Craig	O
Finseth	O
,	O
author	O
of	O
The	O
Craft	O
of	O
Text	B-Application
Editing	I-Application
,	O
TECO	B-Application
has	O
been	O
described	O
as	O
a	O
"	O
write-only	O
"	O
language	O
,	O
implying	O
that	O
once	O
a	O
program	O
is	O
written	O
in	O
TECO	B-Application
,	O
it	O
is	O
extremely	O
difficult	O
to	O
comprehend	O
what	O
it	O
did	O
without	O
appropriate	O
documentation	O
.	O
</s>
<s>
Despite	O
its	B-Application
syntax	B-Application
,	O
the	O
TECO	B-Application
command	O
language	O
was	O
tremendously	O
powerful	O
,	O
and	O
clones	O
are	O
still	O
available	O
for	O
MS-DOS	B-Application
and	O
for	O
Unix	B-Application
.	O
</s>
<s>
TECO	B-Application
commands	O
are	O
characters	O
(	O
including	O
control-characters	O
)	O
,	O
and	O
the	O
prompt	O
is	O
a	O
single	O
asterisk	O
:	O
</s>
<s>
one	O
could	O
use	O
the	O
following	O
TECO	B-Application
session	O
(	O
noting	O
that	O
the	O
prompt	O
is	O
"	O
*	O
"	O
and	O
"	O
$	O
"	O
is	O
how	O
ESC	O
is	O
echoed	O
)	O
to	O
change	O
"	O
Hello	O
"	O
into	O
"	O
Goodbye	O
"	O
:	O
</s>
<s>
These	O
two	O
example	O
programs	O
are	O
a	O
simple	O
interchange	O
sort	O
of	O
the	O
current	O
text	O
buffer	O
,	O
based	O
on	O
the	O
1st	O
character	O
of	O
each	O
line	O
,	O
taken	O
from	O
the	O
PDP-11	O
TECO	B-Application
User	O
's	O
Guide	O
.	O
</s>
<s>
A	O
"	O
goto	B-Application
"	O
and	O
"	O
structured	B-Language
"	O
version	O
are	O
shown	O
.	O
</s>
