<s>
GNU	B-Application
Screen	I-Application
is	O
a	O
terminal	B-General_Concept
multiplexer	O
,	O
a	O
software	B-Application
application	I-Application
that	O
can	O
be	O
used	O
to	O
multiplex	B-Architecture
several	O
virtual	B-Application
consoles	I-Application
,	O
allowing	O
a	O
user	O
to	O
access	O
multiple	O
separate	O
login	B-Operating_System
sessions	I-Operating_System
inside	O
a	O
single	O
terminal	B-General_Concept
window	O
,	O
or	O
detach	O
and	O
reattach	O
sessions	O
from	O
a	O
terminal	B-General_Concept
.	O
</s>
<s>
It	O
is	O
useful	O
for	O
dealing	O
with	O
multiple	O
programs	O
from	O
a	O
command	B-Application
line	I-Application
interface	I-Application
,	O
and	O
for	O
separating	O
programs	O
from	O
the	O
session	O
of	O
the	O
Unix	B-Application
shell	I-Application
that	O
started	O
the	O
program	O
,	O
particularly	O
so	O
a	O
remote	O
process	B-Operating_System
continues	O
running	O
even	O
when	O
the	O
user	O
is	O
disconnected	O
.	O
</s>
<s>
Released	O
under	O
the	O
terms	O
of	O
version	O
3	O
or	O
later	O
of	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
,	O
GNU	B-Application
Screen	I-Application
is	O
free	B-Application
software	I-Application
.	O
</s>
<s>
GNU	B-Application
Screen	I-Application
can	O
be	O
thought	O
of	O
as	O
a	O
text	B-Application
version	I-Application
of	O
graphical	O
window	B-Application
managers	I-Application
,	O
or	O
as	O
a	O
way	O
of	O
putting	O
virtual	O
terminals	O
into	O
any	O
login	B-Operating_System
session	I-Operating_System
.	O
</s>
<s>
Screen	O
is	O
often	O
used	O
when	O
a	O
network	O
connection	O
to	O
the	O
terminal	B-General_Concept
is	O
unreliable	O
,	O
as	O
a	O
dropped	O
network	O
connection	O
typically	O
terminates	O
all	O
programs	O
the	O
user	O
was	O
running	O
(	O
child	O
processes	O
of	O
the	O
login	B-Operating_System
session	I-Operating_System
)	O
,	O
due	O
to	O
the	O
session	O
ending	O
and	O
sending	O
a	O
"	O
hangup	O
"	O
signal	O
(	O
SIGHUP	B-General_Concept
)	O
to	O
all	O
the	O
child	O
processes	O
.	O
</s>
<s>
Running	O
the	O
applications	O
under	O
screen	O
means	O
that	O
the	O
session	O
does	O
not	O
terminate	O
–	O
only	O
the	O
now-defunct	O
terminal	B-General_Concept
gets	O
detached	O
–	O
so	O
applications	O
do	O
n't	O
even	O
know	O
the	O
terminal	B-General_Concept
has	O
detached	O
,	O
and	O
allows	O
the	O
user	O
to	O
reattach	O
the	O
session	O
later	O
and	O
continue	O
working	O
from	O
where	O
they	O
left	O
off	O
.	O
</s>
<s>
Design	O
criteria	O
included	O
VT100	B-Device
emulation	O
(	O
including	O
ANSI	O
X3.64	O
(	O
ISO	O
6429	O
)	O
and	O
ISO	O
2022	O
)	O
and	O
reasonable	O
performance	O
for	O
heavy	O
daily	O
use	O
when	O
character-based	O
terminals	O
were	O
still	O
common	O
.	O
</s>
<s>
Around	O
1990	O
,	O
Laumann	O
handed	O
over	O
maintenance	O
of	O
the	O
code	O
to	O
Jürgen	O
Weigert	O
and	O
Michael	O
Schroeder	O
at	O
the	O
University	O
of	O
Erlangen	O
–	O
Nuremberg	O
,	O
who	O
later	O
moved	O
the	O
project	O
to	O
the	B-Application
GNU	I-Application
Project	I-Application
and	O
added	O
features	O
such	O
as	O
scrollback	O
,	O
split-screen	O
,	O
copy-and-paste	B-General_Concept
,	O
and	O
screen	B-Protocol
sharing	I-Protocol
.	O
</s>
<s>
In	O
May	O
2015	O
,	O
on	O
openSUSE	O
Conference	O
,	O
Jürgen	O
Weigert	O
invited	O
Alexander	O
Naumov	O
to	O
help	O
to	O
develop	O
and	O
maintain	O
GNU	B-Application
screen	I-Application
.	O
</s>
<s>
Two	O
months	O
later	O
with	O
Alex	O
's	O
help	O
GNU	B-Application
screen	I-Application
4.3.0	O
was	O
released	O
.	O
</s>
