<s>
TNSDL	B-Language
stands	O
for	O
TeleNokia	O
Specification	B-Application
and	I-Application
Description	I-Application
Language	I-Application
.	O
</s>
<s>
TNSDL	B-Language
is	O
based	O
on	O
the	O
ITU-T	O
SDL-88	O
language	O
.	O
</s>
<s>
TNSDL	B-Language
is	O
a	O
general-purpose	O
procedural	B-Application
programming	I-Application
language	I-Application
.	O
</s>
<s>
As	O
the	O
world	O
shifted	O
towards	O
packet-switched	O
and	O
internet-based	O
telecommunication	O
,	O
TNSDL	B-Language
turned	O
out	O
to	O
be	O
an	O
excellent	O
fit	O
for	O
developing	O
internet	O
servers	O
,	O
too	O
.	O
</s>
<s>
TNSDL	B-Language
is	O
a	O
very	O
simple	O
,	O
easy-to-learn	O
programming	O
language	O
.	O
</s>
<s>
TNSDL	B-Language
is	O
a	O
strongly	O
typed	O
procedural	B-Application
programming	I-Application
language	I-Application
.	O
</s>
<s>
Its	O
basic	O
capabilities	O
are	O
comparable	O
to	O
the	O
C	B-Language
and	O
Pascal	B-Application
languages	I-Application
.	O
</s>
<s>
In	O
TNSDL	B-Language
processes	O
are	O
created	O
by	O
the	O
CREATE	O
command	O
.	O
</s>
<s>
(	O
It	O
is	O
somewhat	O
similar	O
to	O
the	O
POSIX	O
fork	B-Language
or	O
pthread_create	B-Operating_System
commands	O
.	O
)	O
</s>
<s>
The	O
CREATE	O
command	O
creates	O
either	O
an	O
operating	O
system	O
process	O
or	O
a	O
cooperative	B-Operating_System
task	I-Operating_System
.	O
</s>
<s>
Still	O
,	O
to	O
avoid	O
certain	O
race	B-Operating_System
conditions	I-Operating_System
,	O
developers	O
may	O
need	O
to	O
be	O
prepared	O
for	O
parallel	O
execution	O
.	O
</s>
<s>
TNSDL	B-Language
explicitly	O
supports	O
critical	B-Operating_System
sections	I-Operating_System
to	O
be	O
marked	O
in	O
the	O
code	O
.	O
</s>
<s>
In	O
case	O
of	O
cooperative	B-Operating_System
multitasking	I-Operating_System
a	O
program	O
is	O
scheduled	O
as	O
one	O
operating	O
system	O
process	O
.	O
</s>
<s>
The	O
feature	O
of	O
TNSDL	B-Language
is	O
the	O
actor	B-Application
model	I-Application
.	O
</s>
<s>
Processes	O
are	O
meant	O
to	O
be	O
designed	O
as	O
event-driven	B-Application
finite	I-Application
state	I-Application
machines	I-Application
.	O
</s>
<s>
Inter-process	B-Operating_System
communication	I-Operating_System
is	O
done	O
by	O
asynchronous	O
message	B-Architecture
passing	I-Architecture
.	O
</s>
<s>
Timers	O
,	O
from	O
TNSDL	B-Language
perspective	O
,	O
are	O
delayed	O
messages	O
.	O
</s>
<s>
TNSDL	B-Language
allows	O
inputs	O
to	O
be	O
tied	O
to	O
several	O
or	O
all	O
of	O
the	O
states	O
.	O
</s>
<s>
The	O
concepts	O
of	O
modules	O
and	O
services	O
were	O
added	O
in	O
TNSDL	B-Language
(	O
the	O
service	O
concept	O
of	O
SDL-88	O
is	O
similar	O
to	O
the	O
subautomaton	O
feature	O
of	O
TNSDL	B-Language
)	O
.	O
</s>
<s>
Some	O
elements	O
have	O
been	O
renamed	O
(	O
for	O
example	O
Priority	O
Inputs	O
are	O
called	O
Input	O
Internals	O
in	O
TNSDL	B-Language
)	O
.	O
</s>
<s>
In	O
TNSDL	B-Language
the	O
MACRO	O
feature	O
has	O
been	O
omitted	O
and	O
a	O
WHILE	O
construct	O
has	O
been	O
added	O
to	O
allow	O
loops	O
in	O
a	O
structured	O
way	O
without	O
using	O
JOINs	O
.	O
</s>
<s>
TNSDL	B-Language
is	O
not	O
directly	O
compiled	B-Language
to	O
machine	O
code	O
.	O
</s>
<s>
Instead	O
,	O
TNSDL	B-Language
programs	O
are	O
translated	O
to	O
C	B-Language
language	I-Language
source	O
code	O
.	O
</s>
<s>
The	O
responsibility	O
of	O
TNSDL	B-Language
is	O
to	O
allow	O
message	O
handling	O
,	O
state	O
machine	O
definitions	O
,	O
synchronizing	O
parallel	O
execution	O
,	O
"	O
data	O
warming	O
"	O
etc	O
.	O
</s>
<s>
The	O
task	O
of	O
processor-specific	O
code	O
generation	O
and	O
low-level	O
optimization	O
is	O
delegated	O
to	O
the	O
C	B-Language
compiler	B-Language
used	O
.	O
</s>
<s>
After	O
translating	O
TNSDL	B-Language
to	O
C	B-Language
,	O
any	O
standard-compliant	O
C	B-Language
compiler	B-Language
,	O
linker	O
,	O
coverage	O
measurement	O
and	O
profiling	O
tool	O
can	O
be	O
used	O
.	O
</s>
<s>
To	O
make	O
source-level	O
debugging	O
possible	O
TNSDL	B-Language
puts	O
line	O
number	O
references	O
to	O
the	O
generated	O
C	B-Language
code	O
.	O
</s>
<s>
TNSDL	B-Language
code	O
can	O
call	O
routines	O
implemented	O
in	O
other	O
languages	O
,	O
if	O
objects	O
or	O
libraries	O
are	O
present	O
for	O
them	O
.	O
</s>
<s>
Even	O
C	B-Language
language	I-Language
macros	I-Language
can	O
be	O
used	O
,	O
if	O
C	B-Language
header	O
files	O
are	O
present	O
.	O
</s>
<s>
External	O
declarations	O
must	O
be	O
made	O
available	O
to	O
the	O
TNSDL	B-Language
translator	O
.	O
</s>
<s>
The	O
TNSDL	B-Language
translator	O
is	O
a	O
proprietary	O
tool	O
.	O
</s>
<s>
A	O
source	O
code	O
(	O
reachability	O
)	O
analyser	O
has	O
also	O
been	O
developed	O
specifically	O
for	O
TNSDL	B-Language
.	O
</s>
<s>
TNSDL	B-Language
is	O
commonly	O
used	O
on	O
the	O
DX	B-Device
200	I-Device
,	O
IPA	O
2800	O
and	O
Linux	O
platforms	O
for	O
high-performance	O
,	O
high-availability	O
applications	O
.	O
</s>
<s>
TNSDL	B-Language
is	O
an	O
actively	O
used	O
and	O
developed	O
programming	O
language	O
used	O
by	O
thousands	O
of	O
developers	O
(	O
in	O
2010	O
)	O
.	O
</s>
<s>
TNSDL	B-Language
is	O
mainly	O
used	O
at	O
Nokia	O
Networks	O
for	O
developing	O
software	O
for	O
SGSNs	O
,	O
BSCs	O
,	O
mobile	B-Device
switching	I-Device
centers	I-Device
,	O
application	B-Application
servers	I-Application
both	O
in	O
traditional	O
setups	O
and	O
as	O
virtual	O
network	O
functions	O
(	O
VNF	O
)	O
of	O
NFV	B-Architecture
solutions	O
.	O
</s>
<s>
Despite	O
the	O
difference	O
in	O
syntax	O
,	O
probably	O
one	O
of	O
the	O
closest	O
relative	O
of	O
TNSDL	B-Language
is	O
Go	B-Application
language	I-Application
.	O
</s>
<s>
Both	O
languages	O
has	O
light-weight	B-Operating_System
processes	I-Operating_System
in	O
their	O
focus	O
.	O
</s>
<s>
Go	O
's	O
channel	O
are	O
similar	O
to	O
TNSDL	B-Language
INPUTs	O
and	O
Go	O
's	O
select	O
statement	O
on	O
channels	O
allows	O
very	O
similar	O
program	O
design	O
.	O
</s>
<s>
TNSDL	B-Language
uses	O
asynchronous	O
message	B-Architecture
passing	I-Architecture
between	O
actors	B-Application
,	O
while	O
channels	O
in	O
Go	O
can	O
either	O
be	O
synchronous	O
or	O
asynchronous	O
(	O
buffered	O
)	O
.	O
</s>
<s>
TNSDL	B-Language
allows	O
message	B-Architecture
passing	I-Architecture
between	O
processes	O
running	O
on	O
the	O
same	O
or	O
separate	O
computer	O
nodes	O
.	O
</s>
<s>
In	O
that	O
aspect	O
TNSDL	B-Language
is	O
a	O
relative	O
of	O
Erlang	B-Operating_System
.	O
</s>
<s>
Even	O
though	O
in	O
TNSDL	B-Language
one	O
can	O
define	O
operators	O
for	O
types	O
and	O
protect	O
structure	O
attributes	O
to	O
be	O
accessible	O
via	O
those	O
operators	O
only	O
,	O
TNSDL	B-Language
is	O
not	O
an	O
object-oriented	B-Language
language	I-Language
.	O
</s>
<s>
In	O
that	O
aspect	O
it	O
belongs	O
to	O
the	O
family	O
of	O
non-OOP	O
procedural	B-Application
programming	I-Application
languages	I-Application
,	O
such	O
as	O
C	B-Language
language	I-Language
.	O
</s>
<s>
1980s	O
:	O
In	O
the	O
beginning	O
,	O
ITU-T	O
SDL	B-Application
had	O
a	O
graphical	O
syntax	O
.	O
</s>
<s>
1990	O
:	O
ITU-T	O
SDL	B-Application
shifted	O
towards	O
text-based	O
representation	O
.	O
</s>
<s>
Based	O
on	O
the	O
SDL-88	O
specification	O
TNSDL	B-Language
was	O
born	O
.	O
</s>
<s>
TNSDL	B-Language
is	O
a	O
simplified	O
and	O
heavily	O
customized	O
variant	O
of	O
SDL-88	O
.	O
</s>
