<s>
ManaGeR	O
or	O
MGR	O
was	O
an	O
early	O
windowing	B-Application
system	I-Application
originally	O
designed	O
and	O
developed	O
for	O
Sun	O
computers	O
in	O
1984	O
by	O
Stephen	O
A	O
.	O
Uhler	O
,	O
then	O
at	O
Bellcore	O
.	O
</s>
<s>
MGR	O
featured	O
overlapped	O
,	O
asynchronous	O
windows	O
and	O
an	O
applications	B-Application
interface	O
that	O
was	O
both	O
machine	O
and	O
network	O
independent	O
.	O
</s>
<s>
It	O
was	O
controlled	O
by	O
mousing	O
pop-up	O
menus	O
,	O
by	O
keyboard	O
interaction	O
,	O
and	O
by	O
escape	O
sequences	O
written	O
on	O
pseudo-terminals	B-Protocol
by	O
client	O
software	O
.	O
</s>
<s>
The	O
system	O
was	O
presented	O
at	O
the	O
USENIX	B-Operating_System
Fourth	O
Computer	O
Graphics	O
Workshop	O
in	O
1987	O
as	O
"	O
MGR	O
-	O
a	O
Window	B-Application
System	I-Application
for	O
UNIX	O
"	O
.	O
</s>
<s>
The	O
entire	O
MGR	O
source	O
code	O
was	O
posted	O
to	O
the	O
comp.sources.unix	O
Usenet	B-Application
newsgroup	O
,	O
Volume	O
17	O
,	O
Issue	O
1	O
,	O
in	O
January	O
1989	O
.	O
</s>
<s>
termcap-style	O
terminal	O
control	O
functions	O
,	O
graphics	O
primitives	O
such	O
as	O
line	O
and	O
circle	O
drawing	O
;	O
</s>
<s>
commands	O
to	O
reshape	O
and	O
position	O
windows	O
;	O
and	O
a	O
message	B-Architecture
passing	I-Architecture
facility	O
enabling	O
client	O
programs	O
to	O
rendezvous	O
and	O
exchange	O
messages	O
.	O
</s>
<s>
Client	O
programs	O
may	O
ask	O
to	O
be	O
informed	O
when	O
a	O
change	O
in	O
the	O
window	B-Application
system	I-Application
occurs	O
,	O
such	O
as	O
a	O
reshaped	O
window	O
,	O
a	O
pushed	O
mouse	B-Device
button	O
,	O
or	O
a	O
message	O
sent	O
from	O
another	O
client	O
program	O
.	O
</s>
<s>
These	O
changes	O
are	O
called	O
events	B-Application
.	O
</s>
<s>
MGR	O
notifies	O
a	O
client	O
program	O
of	O
an	O
event	O
by	O
sending	O
it	O
an	O
ASCII	B-Protocol
character	I-Protocol
string	O
in	O
a	O
format	O
specified	O
by	O
the	O
client	O
program	O
.	O
</s>
<s>
Existing	O
applications	B-Application
can	O
be	O
integrated	O
into	O
the	O
windowing	B-Application
environment	I-Application
without	O
modification	O
by	O
having	O
MGR	O
imitate	O
keystrokes	O
in	O
response	O
to	O
user	O
defined	O
menu	O
selections	O
or	O
other	O
events	B-Application
.	O
</s>
<s>
Bitmap	O
heavy	O
applications	B-Application
would	O
often	O
download	O
bitmaps	O
to	O
be	O
used	O
at	O
application	O
start	O
,	O
which	O
could	O
make	O
an	O
application	O
look	O
like	O
it	O
was	O
hung	O
.	O
</s>
<s>
Since	O
applications	B-Application
used	O
input	O
and	O
output	O
streams	O
,	O
there	O
could	O
be	O
problems	O
when	O
unexpected	O
input	O
arrived	O
,	O
say	O
from	O
line	O
noise	O
or	O
from	O
a	O
system	O
message	O
.	O
</s>
<s>
MGR	O
ran	O
on	O
at	O
least	O
these	O
systems	O
:	O
SunOS	B-Operating_System
on	O
Sun	O
workstations	O
(	O
the	O
original	O
development	O
platform	O
)	O
,	O
Apple	B-Device
Macintosh	I-Device
,	O
Unix	O
System	O
V	O
on	O
the	O
AT&T	B-Device
UNIX	I-Device
PC	I-Device
,	O
Ultrix	B-Operating_System
on	O
the	O
DECstation	B-Device
3100	I-Device
,	O
MiNT	B-Application
on	O
the	O
Atari	B-Device
ST	I-Device
,	O
OS-9	B-Operating_System
,	O
Coherent	B-Operating_System
,	O
Linux	B-Application
,	O
FreeBSD	B-Operating_System
and	O
VSTa	O
.	O
</s>
<s>
The	O
initial	O
Macintosh	B-Device
port	O
was	O
done	O
on	O
a	O
Macintosh	B-Device
Plus	I-Device
computer	O
using	O
the	O
Lightspeed	B-Operating_System
C	I-Operating_System
compiler	O
.	O
</s>
<s>
It	O
was	O
a	O
hybrid	O
port	O
in	O
that	O
many	O
of	O
the	O
low-level	O
operations	O
were	O
passed	O
on	O
to	O
QuickDraw	B-Operating_System
instead	O
of	O
using	O
the	O
internal	O
bitmap	O
code	O
.	O
</s>
<s>
The	O
application	O
did	O
not	O
conform	O
to	O
the	O
Macintosh	B-Device
user	O
interface	O
guidelines	O
as	O
it	O
took	O
over	O
the	O
entire	O
screen	O
.	O
</s>
