<s>
Master/slave	B-Operating_System
is	O
a	O
model	O
of	O
asymmetric	O
communication	O
or	O
control	O
where	O
one	O
device	B-Architecture
or	O
process	B-Operating_System
(	O
the	O
"	O
master	O
"	O
)	O
controls	O
one	O
or	O
more	O
other	O
devices	O
or	O
processes	O
(	O
the	O
"	O
slaves	O
"	O
)	O
and	O
serves	O
as	O
their	O
communication	O
hub	O
.	O
</s>
<s>
The	O
master/slave	B-Operating_System
terminology	I-Operating_System
was	O
first	O
used	O
in	O
1904	O
.	O
</s>
<s>
In	O
electronics	O
,	O
master/slave	B-Operating_System
relationships	O
are	O
used	O
to	O
describe	O
some	O
of	O
the	O
following	O
scenarios	O
:	O
</s>
<s>
In	O
parallel	B-Protocol
ATA	I-Protocol
hard	B-Device
drive	I-Device
arrangements	O
,	O
the	O
terms	O
master	O
and	O
slave	O
are	O
used	O
to	O
describe	O
drives	O
on	O
the	O
same	O
cable	O
,	O
but	O
neither	O
drive	O
has	O
control	O
or	O
priority	O
over	O
the	O
other	O
.	O
</s>
<s>
In	O
AXI	B-Protocol
,	O
master	O
and	O
slave	O
have	O
differing	O
roles	O
,	O
with	O
master	O
initiating	O
transactions	O
and	O
the	O
slave	O
responding	O
to	O
those	O
transactions	O
.	O
</s>
<s>
A	O
Serial	B-Architecture
Peripheral	I-Architecture
Interface	I-Architecture
bus	I-Architecture
typically	O
has	O
a	O
single	O
master	O
controlling	O
multiple	O
slaves	O
.	O
</s>
<s>
and	O
discontinuing	O
the	O
use	O
of	O
master/slave	B-Operating_System
terms	O
.	O
</s>
<s>
Edge-triggered	O
flip-flops	O
can	O
be	O
created	O
by	O
arranging	O
two	O
latches	O
(	O
master	O
latch	O
and	O
slave	O
latch	O
)	O
in	O
a	O
master/slave	B-Operating_System
configuration	O
.	O
</s>
<s>
In	O
database	B-General_Concept
replication	I-General_Concept
,	O
the	O
master	O
database	O
is	O
regarded	O
as	O
the	O
authoritative	O
source	O
,	O
and	O
the	O
slave	O
(	O
also	O
called	O
replica	O
)	O
databases	O
are	O
synchronized	O
to	O
it	O
.	O
</s>
<s>
In	O
photography	O
,	O
secondary	O
or	O
slave	O
flash	O
units	O
may	O
be	O
synchronized	O
to	O
the	O
master	B-Operating_System
unit	I-Operating_System
to	O
provide	O
light	O
from	O
additional	O
directions	O
.	O
</s>
<s>
Duplication	O
is	O
often	O
done	O
with	O
several	O
cassette	B-Device
tapes	I-Device
or	O
compact	O
disc	O
recorders	O
linked	O
together	O
.	O
</s>
<s>
Railway	O
locomotives	O
operating	O
in	O
multiple	O
(	O
for	O
example	O
:	O
to	O
pull	O
loads	O
too	O
heavy	O
for	O
a	O
single	O
locomotive	O
)	O
can	O
be	O
referred	O
to	O
as	O
a	O
master/slave	B-Operating_System
configuration	O
with	O
the	O
operation	O
of	O
all	O
locomotives	O
in	O
the	O
train	O
slaved	O
to	O
the	O
controls	O
of	O
the	O
first	O
locomotive	O
.	O
</s>
<s>
In	O
automotive	O
engineering	O
,	O
the	O
master	O
cylinder	O
is	O
a	O
control	O
device	B-Architecture
that	O
converts	O
force	O
into	O
hydraulic	O
pressure	O
in	O
the	O
brake	O
system	O
.	O
</s>
<s>
This	O
device	B-Architecture
controls	O
slave	O
cylinders	O
located	O
at	O
the	O
other	O
end	O
of	O
the	O
hydraulic	O
system	O
.	O
</s>
<s>
The	O
master/slave	B-Operating_System
terminology	I-Operating_System
was	O
used	O
in	O
1988	O
for	O
RFC	O
1059	O
and	O
in	O
1997	O
for	O
RFC	O
2136	O
,	O
related	O
to	O
the	O
domain	B-Application
name	I-Application
system	I-Application
.	O
</s>
<s>
I	O
introduced	O
the	O
master/slave	B-Operating_System
terminology	I-Operating_System
in	O
RFC	O
2136	O
,	O
because	O
I	O
needed	O
names	O
for	O
the	O
roles	O
in	O
an	O
AXFR/IXFR	B-Protocol
transaction	I-Protocol
,	O
and	O
the	O
zone	B-Protocol
transfer	I-Protocol
hierarchy	O
could	O
be	O
more	O
than	O
one	O
layer	O
deep	O
,	O
such	O
that	O
a	O
server	O
might	O
initiate	O
some	O
AXFR/IXFR	O
'	O
s	O
to	O
the	O
"	O
primary	O
master	O
"	O
but	O
then	O
respond	O
to	O
AXFR/IXFR	O
'	O
s	O
from	O
other	O
servers	O
.	O
</s>
<s>
In	O
2018	O
,	O
after	O
a	O
heated	O
debate	O
,	O
developers	O
of	O
the	O
Python	B-Language
programming	I-Language
language	I-Language
replaced	O
the	O
term	O
.	O
</s>
<s>
Google	B-Application
's	I-Application
developer	O
documentation	O
style	O
guide	O
recommends	O
avoiding	O
the	O
term	O
master	O
in	O
software	O
documentation	O
,	O
especially	O
in	O
combination	O
with	O
slave	O
.	O
</s>
<s>
In	O
2020	O
,	O
GitHub	O
replaced	O
the	O
default	O
'	O
master	O
 '	O
git	B-Application
branch	O
with	O
'	O
main	O
 '	O
.	O
</s>
<s>
Other	O
replacement	O
names	O
include	O
'	O
default	O
 '	O
,	O
'	O
primary	O
 '	O
,	O
'	O
controller	O
 '	O
,	O
'	O
root	O
 '	O
,	O
'	O
initiator	O
 '	O
,	O
'	O
leader	O
 '	O
,	O
'	O
director	O
 '	O
;	O
and	O
for	O
'	O
slave	O
 '	O
:	O
'	O
performer	O
 '	O
,	O
'	O
worker	O
 '	O
,	O
'	O
peripheral	O
 '	O
,	O
'	O
responder	O
 '	O
,	O
'	O
device	B-Architecture
 '	O
,	O
'	O
replica	O
 '	O
,	O
'	O
satellite	O
 '	O
,	O
and	O
'	O
secondary	O
 '	O
.	O
</s>
<s>
Python	B-Language
switched	O
to	O
'	O
main	O
 '	O
,	O
'	O
parent	O
 '	O
,	O
and	O
'	O
server	O
 '	O
;	O
and	O
'	O
worker	O
 '	O
,	O
'	O
child	O
 '	O
,	O
and	O
'	O
helper	O
 '	O
,	O
depending	O
on	O
context	O
.	O
</s>
<s>
The	O
Linux	B-Operating_System
kernel	I-Operating_System
has	O
adopted	O
a	O
similar	O
policy	O
to	O
use	O
more	O
specific	O
terms	O
in	O
new	O
code	O
or	O
documentation	O
.	O
</s>
