<s>
Sketchpad	B-Application
(	O
a.k.a.	O
</s>
<s>
It	O
pioneered	O
human	O
–	O
computer	O
interaction	O
(	O
HCI	O
)	O
,	O
and	O
is	O
considered	O
the	O
ancestor	O
of	O
modern	O
computer-aided	B-Application
design	I-Application
(	O
CAD	B-Application
)	O
programs	O
as	O
well	O
as	O
a	O
major	O
breakthrough	O
in	O
the	O
development	O
of	O
computer	O
graphics	O
in	O
general	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
was	O
derived	O
from	O
Sketchpad	B-Application
as	O
well	O
as	O
modern	O
object-oriented	B-Language
programming	I-Language
.	O
</s>
<s>
Using	O
the	O
program	O
,	O
Ivan	O
Sutherland	O
showed	O
that	O
computer	O
graphics	O
could	O
be	O
used	O
for	O
both	O
artistic	O
and	O
technical	B-Application
purposes	O
in	O
addition	O
to	O
demonstrating	O
a	O
novel	O
method	O
of	O
human	O
–	O
computer	O
interaction	O
.	O
</s>
<s>
Sutherland	O
was	O
inspired	O
by	O
the	O
Memex	B-General_Concept
from	O
"	O
As	O
We	O
May	O
Think	O
"	O
by	O
Vannevar	O
Bush	O
.	O
</s>
<s>
Sketchpad	B-Application
inspired	O
Douglas	O
Engelbart	O
to	O
design	O
and	O
develop	O
oN-Line	O
System	O
at	O
the	O
Augmentation	O
Research	O
Center	O
(	O
ARC	O
)	O
at	O
the	O
Stanford	O
Research	O
Institute	O
(	O
SRI	O
)	O
during	O
the	O
1960s	O
.	O
</s>
<s>
See	O
History	O
of	O
the	O
graphical	B-Application
user	I-Application
interface	I-Application
for	O
a	O
more	O
detailed	O
discussion	O
of	O
GUI	B-Application
development	O
.	O
</s>
<s>
Sketchpad	B-Application
was	O
the	O
earliest	O
program	O
ever	O
to	O
utilize	O
a	O
complete	O
graphical	B-Application
user	I-Application
interface	I-Application
.	O
</s>
<s>
The	O
clever	O
way	O
the	O
program	O
organized	O
its	O
geometric	O
data	O
pioneered	O
the	O
use	O
of	O
"	O
master	O
"	O
(	O
"	O
objects	O
"	O
)	O
and	O
"	O
occurrences	O
"	O
(	O
"	O
instances	O
"	O
)	O
in	O
computing	O
and	O
pointed	O
forward	O
to	O
object	B-Language
oriented	I-Language
programming	I-Language
.	O
</s>
<s>
Geometric	O
constraints	O
was	O
another	O
major	O
invention	O
in	O
Sketchpad	B-Application
,	O
letting	O
the	O
user	O
easily	O
constrain	O
geometric	O
properties	O
in	O
the	O
drawingfor	O
instance	O
,	O
the	O
length	O
of	O
a	O
line	O
or	O
the	O
angle	O
between	O
two	O
lines	O
could	O
be	O
fixed	O
.	O
</s>
<s>
As	O
a	O
trade	O
magazine	O
said	O
,	O
clearly	O
Sutherland	O
"	O
broke	O
new	O
ground	O
in	O
3D	O
computer	O
modeling	O
and	O
visual	O
simulation	O
,	O
the	O
basis	O
for	O
computer	O
graphics	O
and	O
CAD/CAM	O
"	O
.	O
</s>
<s>
Patrick	O
J	O
.	O
Hanratty	O
is	O
sometimes	O
called	O
the	O
"	O
father	O
of	O
CAD/CAM	O
"	O
and	O
wrote	O
PRONTO	O
,	O
a	O
numerical	O
control	O
language	O
at	O
General	O
Electric	O
in	O
1957	O
,	O
and	O
wrote	O
CAD	B-Application
software	I-Application
while	O
working	O
for	O
General	O
Motors	O
beginning	O
in	O
1961	O
.	O
</s>
<s>
Sutherland	O
wrote	O
in	O
his	O
thesis	O
that	O
Bolt	O
,	O
Beranek	O
and	O
Newman	O
had	O
a	O
"	O
similar	O
program	O
"	O
and	O
T-Square	B-Application
was	O
developed	O
by	O
Peter	O
Samson	O
and	O
one	O
or	O
more	O
fellow	O
MIT	O
students	O
in	O
1962	O
,	O
both	O
for	O
the	O
PDP-1	B-Device
.	O
</s>
<s>
The	O
Computer	O
History	O
Museum	O
holds	O
program	O
listings	O
for	O
Sketchpad	B-Application
.	O
</s>
<s>
Sketchpad	B-Application
ran	O
on	O
the	O
Lincoln	B-Device
TX-2	I-Device
(	O
1958	O
)	O
computer	O
at	O
MIT	O
,	O
which	O
had	O
64k	O
of	O
36-bit	O
words	O
.	O
</s>
<s>
The	O
user	O
drew	O
on	O
the	O
screen	O
with	O
the	O
recently	O
invented	O
light	B-Device
pen	I-Device
,	O
which	O
relayed	O
information	O
on	O
its	O
position	O
by	O
computing	O
at	O
what	O
time	O
the	O
light	O
from	O
the	O
scanning	O
Cathode-ray	B-Device
tube	I-Device
screen	O
is	O
detected	O
.	O
</s>
<s>
In	O
order	O
to	O
configure	O
the	O
initial	O
position	O
of	O
the	O
light	B-Device
pen	I-Device
,	O
the	O
word	O
"	O
INK	O
"	O
is	O
displayed	O
on	O
the	O
screen	O
,	O
which	O
,	O
upon	O
tapping	O
,	O
initialised	O
the	O
program	O
with	O
a	O
white	O
cross	O
to	O
continue	O
keeping	O
track	O
of	O
the	O
pen	O
's	O
movement	O
relative	O
to	O
its	O
previous	O
position	O
.	O
</s>
<s>
The	O
TX-2	B-Device
was	O
an	O
experimental	O
machine	O
and	O
the	O
hardware	O
changed	O
frequently	O
(	O
on	O
Wednesdays	O
,	O
according	O
to	O
Sutherland	O
)	O
.	O
</s>
<s>
By	O
1975	O
,	O
the	O
light	B-Device
pen	I-Device
and	O
the	O
Cathode-ray	B-Device
tube	I-Device
with	O
which	O
it	O
had	O
been	O
used	O
had	O
been	O
removed	O
.	O
</s>
