<s>
Structured	B-Application
concurrency	I-Application
is	O
a	O
programming	O
paradigm	O
aimed	O
at	O
improving	O
the	O
clarity	O
,	O
quality	O
,	O
and	O
development	O
time	O
of	O
a	O
computer	B-Application
program	I-Application
by	O
using	O
a	O
structured	O
approach	O
to	O
concurrent	B-Architecture
programming	I-Architecture
.	O
</s>
<s>
It	O
allows	O
control	O
flow	O
to	O
remain	O
readily	O
evident	O
by	O
the	O
structure	O
of	O
the	O
source	O
code	O
despite	O
the	O
presence	O
of	O
concurrency	B-Architecture
.	O
</s>
<s>
Structured	B-Application
concurrency	I-Application
is	O
analogous	O
to	O
structured	B-Language
programming	I-Language
,	O
which	O
introduced	O
control	O
flow	O
constructs	O
that	O
encapsulated	O
sequential	O
statements	O
and	O
subroutines	O
.	O
</s>
<s>
The	O
fork	B-Operating_System
–	I-Operating_System
join	I-Operating_System
model	I-Operating_System
from	O
the	O
1960s	O
,	O
embodied	O
by	O
multiprocessing	O
tools	O
like	O
OpenMP	B-Application
,	O
is	O
an	O
early	O
example	O
of	O
a	O
system	O
ensuring	O
all	O
threads	O
have	O
completed	O
before	O
exit	O
.	O
</s>
<s>
However	O
,	O
Smith	O
argues	O
that	O
this	O
model	O
is	O
not	O
true	O
structured	B-Application
concurrency	I-Application
as	O
the	O
programming	O
language	O
is	O
unaware	O
of	O
the	O
joining	O
behavior	O
,	O
and	O
is	O
thus	O
unable	O
to	O
enforce	O
safety	O
.	O
</s>
<s>
The	O
concept	O
was	O
formulated	O
in	O
2016	O
by	O
Martin	O
Sústrik	O
(	O
creator	O
of	O
ZeroMQ	B-Operating_System
)	O
with	O
his	O
C	O
library	O
libdill	O
,	O
with	O
goroutines	O
as	O
a	O
starting	O
point	O
.	O
</s>
<s>
It	O
was	O
further	O
refined	O
in	O
2017	O
by	O
Nathaniel	O
J	O
.	O
Smith	O
,	O
who	O
introduced	O
a	O
"	O
nursery	O
pattern	O
"	O
in	O
his	O
Python	B-Language
implementation	O
called	O
Trio	O
.	O
</s>
<s>
Meanwhile	O
,	O
Roman	O
Elizarov	O
independently	O
came	O
upon	O
the	O
same	O
ideas	O
while	O
developing	O
an	O
experimental	O
coroutine	B-Architecture
library	O
for	O
the	O
Kotlin	B-Language
language	I-Language
,	O
which	O
later	O
became	O
a	O
standard	O
library	O
.	O
</s>
<s>
In	O
2021	O
,	O
Swift	B-Application
adopted	O
structured	B-Application
concurrency	I-Application
.	O
</s>
<s>
Later	O
that	O
year	O
,	O
a	O
draft	O
proposal	O
was	O
published	O
to	O
add	O
structured	B-Application
concurrency	I-Application
to	O
Java	B-Language
.	O
</s>
