<s>
Space	B-Application
Travel	I-Application
is	O
an	O
early	O
video	O
game	O
developed	O
by	O
Ken	O
Thompson	O
in	O
1969	O
that	O
simulates	O
travel	O
in	O
the	O
Solar	O
System	O
.	O
</s>
<s>
The	O
game	O
was	O
developed	O
at	O
Bell	O
Labs	O
before	O
the	O
rise	O
of	O
the	O
commercial	O
video	O
game	O
industry	O
in	O
the	O
early	B-Application
history	I-Application
of	I-Application
video	I-Application
games	I-Application
,	O
and	O
was	O
ported	O
during	O
1969	O
from	O
the	O
Multics	B-Application
operating	I-Application
system	I-Application
to	O
the	O
GECOS	B-Application
operating	B-General_Concept
system	I-General_Concept
on	O
the	O
GE	B-Device
635	I-Device
computer	O
,	O
and	O
then	O
to	O
the	O
PDP-7	B-Device
computer	O
.	O
</s>
<s>
As	O
a	O
part	O
of	O
porting	O
the	O
game	O
to	O
the	O
PDP-7	B-Device
,	O
Thompson	O
developed	O
his	O
own	O
operating	B-General_Concept
system	I-General_Concept
,	O
which	O
later	O
formed	O
the	O
core	O
of	O
the	O
Unix	B-Application
operating	I-Application
system	I-Application
.	O
</s>
<s>
Space	B-Application
Travel	I-Application
never	O
spread	O
beyond	O
Bell	O
Labs	O
or	O
had	O
an	O
effect	O
on	O
future	O
games	O
,	O
leaving	O
its	O
primary	O
legacy	O
as	O
part	O
of	O
the	O
original	O
push	O
for	O
the	O
development	O
of	O
Unix	B-Application
.	O
</s>
<s>
Space	B-Application
Travel	I-Application
is	O
a	O
spaceflight	O
simulation	O
video	O
game	O
,	O
presented	O
in	O
a	O
two-dimensional	O
top-down	O
view	O
,	O
with	O
monochrome	O
graphics	O
consisting	O
of	O
white	O
lines	O
on	O
a	O
black	O
background	O
.	O
</s>
<s>
This	O
sometimes	O
results	O
in	O
odd	O
behavior	O
;	O
for	O
example	O
,	O
the	O
gravitational	O
effect	O
of	O
Mars	B-Application
is	O
much	O
stronger	O
than	O
that	O
of	O
its	O
moon	O
Phobos	O
.	O
</s>
<s>
In	O
1969	O
,	O
programmer	O
Ken	O
Thompson	O
worked	O
for	O
Bell	O
Labs	O
on	O
the	O
Multics	B-Application
operating	I-Application
system	I-Application
on	O
a	O
GE	B-Device
645	I-Device
mainframe	B-Architecture
.	O
</s>
<s>
During	O
his	O
work	O
,	O
Thompson	O
developed	O
Space	B-Application
Travel	I-Application
on	O
the	O
system	O
.	O
</s>
<s>
Multics	B-Application
was	O
a	O
collaborative	O
project	O
between	O
several	O
institutions	O
for	O
an	O
interactive	O
,	O
multi-user	O
operating	B-General_Concept
system	I-General_Concept
that	O
provided	O
convenient	O
access	O
for	O
programming	O
.	O
</s>
<s>
Thompson	O
then	O
ported	O
the	O
Space	B-Application
Travel	I-Application
code	O
to	O
Fortran	B-Application
so	O
that	O
it	O
could	O
run	O
on	O
the	O
GECOS	B-Application
operating	B-General_Concept
system	I-General_Concept
already	O
present	O
on	O
the	O
GE	B-Device
645	I-Device
.	O
</s>
<s>
GECOS	B-Application
,	O
however	O
,	O
used	O
an	O
"	O
interactive	O
batch	O
"	O
model	O
,	O
meaning	O
that	O
while	O
several	O
computer	B-General_Concept
terminals	I-General_Concept
were	O
attached	O
to	O
the	O
central	O
computer	O
,	O
each	O
terminal	O
's	O
program	O
jobs	O
had	O
to	O
be	O
submitted	O
in	O
a	O
queue	O
,	O
resulting	O
in	O
long	O
pauses	O
in	O
the	O
game	O
while	O
the	O
GE	B-Device
645	I-Device
worked	O
on	O
jobs	O
for	O
other	O
terminals	O
.	O
</s>
<s>
Thompson	O
learned	O
that	O
a	O
neighboring	O
department	O
had	O
an	O
older	O
,	O
little-used	O
PDP-7	B-Device
minicomputer	B-Architecture
.	O
</s>
<s>
As	O
this	O
machine	O
would	O
solve	O
the	O
problems	O
with	O
playing	O
the	O
game	O
,	O
he	O
ported	O
Space	B-Application
Travel	I-Application
to	O
this	O
platform	O
using	O
a	O
cross	B-Application
compiler	I-Application
on	O
the	O
GECOS	B-Application
system	O
,	O
writing	O
the	O
resulting	O
machine	B-Language
code	I-Language
to	O
punch	O
tape	O
and	O
then	O
loading	O
it	O
into	O
the	O
PDP-7	B-Device
.	O
</s>
<s>
Thompson	O
did	O
not	O
use	O
any	O
of	O
the	O
provided	O
PDP-7	B-Device
code	O
,	O
writing	O
everything	O
from	O
scratch	O
,	O
including	O
a	O
floating	B-Algorithm
point	I-Algorithm
library	O
and	O
other	O
low-level	O
tools	O
.	O
</s>
<s>
The	O
tedium	O
of	O
moving	O
the	O
code	O
between	O
the	O
two	O
machines	O
prompted	O
Thompson	O
to	O
design	O
his	O
own	O
simple	O
file	B-Application
system	I-Application
based	O
on	O
some	O
chalkboard	O
ideas	O
by	O
Dennis	O
Ritchie	O
and	O
Rudd	O
Canaday	O
,	O
rooted	O
in	O
their	O
experience	O
with	O
the	O
Multics	B-Application
file	B-Application
system	I-Application
.	O
</s>
<s>
Before	O
long	O
,	O
it	O
had	O
become	O
a	O
simple	O
operating	B-General_Concept
system	I-General_Concept
of	O
its	O
own	O
.	O
</s>
<s>
Thompson	O
then	O
wrote	O
an	O
assembler	B-Application
for	O
the	O
PDP-7	B-Device
to	O
avoid	O
using	O
the	O
GECOS	B-Application
computer	O
entirely	O
.	O
</s>
<s>
While	O
Thompson	O
continued	O
working	O
on	O
the	O
PDP-7	B-Device
,	O
the	O
original	O
Multics	B-Application
team	O
had	O
concluded	O
that	O
as	O
Bell	O
had	O
exited	O
the	O
Multics	B-Application
program	O
,	O
there	O
was	O
no	O
reason	O
for	O
the	O
company	O
to	O
continue	O
operating	O
the	O
expensive	O
GE	B-Device
645	I-Device
,	O
and	O
they	O
believed	O
it	O
would	O
be	O
removed	O
within	O
a	O
few	O
months	O
.	O
</s>
<s>
They	O
repeatedly	O
asked	O
management	O
for	O
a	O
new	O
machine	O
to	O
continue	O
their	O
operating	B-General_Concept
system	I-General_Concept
work	O
.	O
</s>
<s>
This	O
ultimately	O
culminated	O
in	O
a	O
lengthy	O
proposal	O
to	O
buy	O
some	O
parts	O
and	O
rent	O
others	O
of	O
DEC	O
's	O
new	O
PDP-10	B-Device
system	O
,	O
then	O
US$120	O
,	O
000	O
,	O
but	O
this	O
too	O
was	O
rejected	O
.	O
</s>
<s>
Ritchie	O
later	O
surmised	O
that	O
the	O
company	O
had	O
just	O
exited	O
one	O
operating	B-General_Concept
system	I-General_Concept
project	O
and	O
was	O
in	O
no	O
hurry	O
to	O
spend	O
money	O
to	O
start	O
another	O
.	O
</s>
<s>
The	O
team	O
also	O
changed	O
their	O
proposal	O
;	O
the	O
machine	O
was	O
not	O
being	O
requested	O
to	O
develop	O
an	O
operating	B-General_Concept
system	I-General_Concept
,	O
but	O
a	O
system	O
for	O
"	O
editing	O
and	O
formatting	O
text	O
"	O
,	O
essentially	O
a	O
word	B-General_Concept
processor	I-General_Concept
.	O
</s>
<s>
By	O
this	O
point	O
,	O
the	O
PDP-7	B-Device
was	O
already	O
considered	O
completely	O
obsolete	O
.	O
</s>
<s>
The	O
PDP-11	O
arrived	O
in	O
the	O
summer	O
,	O
without	O
a	O
hard	B-Device
drive	I-Device
,	O
and	O
the	O
entire	O
team	O
began	O
porting	O
the	O
rudimentary	O
operating	B-General_Concept
system	I-General_Concept
from	O
the	O
PDP-7	B-Device
to	O
the	O
new	O
machine	O
.	O
</s>
<s>
During	O
this	O
time	O
it	O
gained	O
the	O
slash-separated	O
hierarchical	O
directories	O
and	O
other	O
features	O
of	O
the	O
Unix	B-Application
system	I-Application
.	O
</s>
<s>
When	O
the	O
hard	B-Device
drive	I-Device
arrived	O
in	O
December	O
the	O
rest	O
of	O
the	O
basic	O
features	O
were	O
added	O
.	O
</s>
<s>
The	O
team	O
was	O
now	O
committed	O
to	O
the	O
new	O
system	O
,	O
and	O
Brian	O
Kernighan	O
gave	O
it	O
the	O
name	O
Unix	B-Application
,	O
a	O
"	O
somewhat	O
treacherous	O
pun	O
"	O
on	O
Multics	B-Application
.	O
</s>
<s>
Space	B-Application
Travel	I-Application
was	O
one	O
of	O
the	O
early	B-Application
mainframe	I-Application
games	I-Application
developed	O
before	O
the	O
rise	O
of	O
the	O
commercial	O
video	O
game	O
industry	O
in	O
the	O
early	B-Application
history	I-Application
of	I-Application
video	I-Application
games	I-Application
,	O
and	O
was	O
never	O
distributed	O
beyond	O
its	O
initial	O
locations	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
it	O
had	O
no	O
effect	O
on	O
future	O
video	O
games	O
,	O
and	O
its	O
primary	O
legacy	O
is	O
that	O
of	O
sparking	O
the	O
creation	O
of	O
Unix	B-Application
.	O
</s>
