<s>
Ada	B-Language
is	O
a	O
structured	B-Language
,	O
statically	O
typed	O
,	O
imperative	B-Application
,	O
and	O
object-oriented	B-Language
high-level	B-Language
programming	I-Language
language	I-Language
,	O
extended	O
from	O
Pascal	B-Application
and	O
other	O
languages	O
.	O
</s>
<s>
It	O
has	O
built-in	O
language	O
support	O
for	O
design	B-Application
by	I-Application
contract	I-Application
(	O
DbC	B-Application
)	O
,	O
extremely	O
strong	O
typing	O
,	O
explicit	O
concurrency	B-Architecture
,	O
tasks	B-General_Concept
,	O
synchronous	B-Architecture
message	I-Architecture
passing	I-Architecture
,	O
protected	O
objects	O
,	O
and	O
non-determinism	O
.	O
</s>
<s>
Ada	B-Language
improves	O
code	O
safety	O
and	O
maintainability	O
by	O
using	O
the	O
compiler	B-Language
to	O
find	O
errors	O
in	O
favor	O
of	O
runtime	B-Library
errors	I-Library
.	O
</s>
<s>
Ada	B-Language
is	O
an	O
international	O
technical	O
standard	O
,	O
jointly	O
defined	O
by	O
the	O
International	O
Organization	O
for	O
Standardization	O
(	O
ISO	O
)	O
,	O
and	O
the	O
International	O
Electrotechnical	O
Commission	O
(	O
IEC	O
)	O
.	O
</s>
<s>
,	O
the	O
standard	O
,	O
called	O
Ada	B-Language
2012	I-Language
informally	O
,	O
is	O
ISO/IEC	O
8652:2012	O
.	O
</s>
<s>
Ada	B-Language
was	O
originally	O
designed	O
by	O
a	O
team	O
led	O
by	O
French	O
computer	O
scientist	O
Jean	O
Ichbiah	O
of	O
Honeywell	O
under	O
contract	O
to	O
the	O
United	O
States	O
Department	O
of	O
Defense	O
(	O
DoD	O
)	O
from	O
1977	O
to	O
1983	O
to	O
supersede	O
over	O
450	O
programming	O
languages	O
used	O
by	O
the	O
DoD	O
at	O
that	O
time	O
.	O
</s>
<s>
Ada	B-Language
was	O
named	O
after	O
Ada	B-General_Concept
Lovelace	I-General_Concept
(	O
1815	O
–	O
1852	O
)	O
,	O
who	O
has	O
been	O
credited	O
as	O
the	O
first	O
computer	O
programmer	O
.	O
</s>
<s>
Ada	B-Language
was	O
originally	O
designed	O
for	O
embedded	B-Architecture
and	O
real-time	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
The	O
Ada95	B-Language
revision	O
,	O
designed	O
by	O
S	O
.	O
Tucker	O
Taft	O
of	O
Intermetrics	O
between	O
1992	O
and	O
1995	O
,	O
improved	O
support	O
for	O
systems	O
,	O
numerical	O
,	O
financial	O
,	O
and	O
object-oriented	B-Language
programming	I-Language
(	O
OOP	O
)	O
.	O
</s>
<s>
Features	O
of	O
Ada	B-Language
include	O
:	O
strong	O
typing	O
,	O
modular	B-Architecture
programming	I-Architecture
mechanisms	O
(	O
packages	O
)	O
,	O
run-time	B-Device
checking	O
,	O
parallel	B-Operating_System
processing	I-Operating_System
(	O
tasks	B-General_Concept
,	O
synchronous	B-Architecture
message	I-Architecture
passing	I-Architecture
,	O
protected	O
objects	O
,	O
and	O
nondeterministic	O
select	O
statements	O
)	O
,	O
exception	B-General_Concept
handling	I-General_Concept
,	O
and	O
generics	B-Language
.	O
</s>
<s>
Ada95	B-Language
added	O
support	O
for	O
object-oriented	B-Language
programming	I-Language
,	O
including	O
dynamic	O
dispatch	O
.	O
</s>
<s>
The	O
syntax	O
of	O
Ada	B-Language
minimizes	O
choices	O
of	O
ways	O
to	O
perform	O
basic	O
operations	O
,	O
and	O
prefers	O
English	O
keywords	O
(	O
such	O
as	O
"	O
or	O
else	O
"	O
and	O
"	O
and	O
then	O
"	O
)	O
to	O
symbols	O
(	O
such	O
as	O
"	O
||	O
"	O
and	O
"	O
&&	O
"	O
)	O
.	O
</s>
<s>
Ada	B-Language
uses	O
the	O
basic	O
arithmetical	O
operators	O
"	O
+	O
"	O
,	O
"	O
-	O
"	O
,	O
"	O
*	O
"	O
,	O
and	O
"	O
/	O
"	O
,	O
but	O
avoids	O
using	O
other	O
symbols	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
conditional	O
blocks	O
this	O
avoids	O
a	O
dangling	O
else	O
that	O
could	O
pair	O
with	O
the	O
wrong	O
nested	O
if-expression	O
in	O
other	O
languages	O
like	O
C	O
or	O
Java	B-Language
.	O
</s>
<s>
Ada	B-Language
is	O
designed	O
for	O
developing	O
very	O
large	O
software	O
systems	O
.	O
</s>
<s>
Ada	B-Language
packages	O
can	O
be	O
compiled	B-Language
separately	O
.	O
</s>
<s>
Ada	B-Language
package	O
specifications	O
(	O
the	O
package	O
interface	O
)	O
can	O
also	O
be	O
compiled	B-Language
separately	O
without	O
the	O
implementation	O
to	O
check	O
for	O
consistency	O
.	O
</s>
<s>
A	O
large	O
number	O
of	O
compile-time	B-Application
checks	O
are	O
supported	O
to	O
help	O
avoid	O
bugs	B-Error_Name
that	O
would	O
not	O
be	O
detectable	O
until	O
run-time	B-Device
in	O
some	O
other	O
languages	O
or	O
would	O
require	O
explicit	O
checks	O
to	O
be	O
added	O
to	O
the	O
source	O
code	O
.	O
</s>
<s>
The	O
adherence	O
to	O
strong	O
typing	O
allows	O
detecting	O
many	O
common	O
software	B-Error_Name
errors	I-Error_Name
(	O
wrong	O
parameters	O
,	O
range	O
violations	O
,	O
invalid	O
references	O
,	O
mismatched	O
types	O
,	O
etc	O
.	O
)	O
</s>
<s>
either	O
during	O
compile-time	B-Application
,	O
or	O
otherwise	O
during	O
run-time	B-Device
.	O
</s>
<s>
As	O
concurrency	B-Architecture
is	O
part	O
of	O
the	O
language	O
specification	O
,	O
the	O
compiler	B-Language
can	O
in	O
some	O
cases	O
detect	O
potential	O
deadlocks	B-Operating_System
.	I-Operating_System
</s>
<s>
Compilers	B-Language
also	O
commonly	O
check	O
for	O
misspelled	O
identifiers	O
,	O
visibility	O
of	O
packages	O
,	O
redundant	O
declarations	O
,	O
etc	O
.	O
</s>
<s>
Ada	B-Language
also	O
supports	O
run-time	B-Device
checks	O
to	O
protect	O
against	O
access	O
to	O
unallocated	O
memory	O
,	O
buffer	B-General_Concept
overflow	I-General_Concept
errors	O
,	O
range	O
violations	O
,	O
off-by-one	B-Error_Name
errors	I-Error_Name
,	O
array	B-Application
access	O
errors	O
,	O
and	O
other	O
detectable	O
bugs	B-Error_Name
.	O
</s>
<s>
These	O
checks	O
can	O
be	O
disabled	O
in	O
the	O
interest	O
of	O
runtime	B-Library
efficiency	O
,	O
but	O
can	O
often	O
be	O
compiled	B-Language
efficiently	O
.	O
</s>
<s>
For	O
these	O
reasons	O
,	O
Ada	B-Language
is	O
widely	O
used	O
in	O
critical	O
systems	O
,	O
where	O
any	O
anomaly	B-Error_Name
might	O
lead	O
to	O
very	O
serious	O
consequences	O
,	O
e.g.	O
,	O
accidental	O
death	O
,	O
injury	O
or	O
severe	O
financial	O
loss	O
.	O
</s>
<s>
Examples	O
of	O
systems	O
where	O
Ada	B-Language
is	O
used	O
include	O
avionics	O
,	O
air	B-Application
traffic	I-Application
control	I-Application
,	O
railways	O
,	O
banking	O
,	O
military	O
and	O
space	O
technology	O
.	O
</s>
<s>
Ada	B-Language
's	O
dynamic	B-General_Concept
memory	I-General_Concept
management	I-General_Concept
is	O
high-level	O
and	O
type-safe	B-Language
.	O
</s>
<s>
Ada	B-Language
has	O
no	O
generic	B-Language
or	O
untyped	O
pointers	O
;	O
nor	O
does	O
it	O
implicitly	O
declare	O
any	O
pointer	O
type	O
.	O
</s>
<s>
Instead	O
,	O
all	O
dynamic	B-General_Concept
memory	I-General_Concept
allocation	I-General_Concept
and	O
deallocation	B-General_Concept
must	O
occur	O
via	O
explicitly	O
declared	O
access	O
types	O
.	O
</s>
<s>
Each	O
access	O
type	O
has	O
an	O
associated	O
storage	O
pool	O
that	O
handles	O
the	O
low-level	O
details	O
of	O
memory	B-General_Concept
management	I-General_Concept
;	O
the	O
programmer	O
can	O
either	O
use	O
the	O
default	O
storage	O
pool	O
or	O
define	O
new	O
ones	O
(	O
this	O
is	O
particularly	O
relevant	O
for	O
Non-Uniform	B-Operating_System
Memory	I-Operating_System
Access	I-Operating_System
)	O
.	O
</s>
<s>
Also	O
,	O
the	O
language	O
provides	O
for	O
accessibility	O
checks	O
,	O
both	O
at	O
compile	B-Application
time	I-Application
and	O
at	O
run	B-Library
time	I-Library
,	O
that	O
ensures	O
that	O
an	O
access	O
value	O
cannot	O
outlive	O
the	O
type	O
of	O
the	O
object	O
it	O
points	O
to	O
.	O
</s>
<s>
Though	O
the	O
semantics	O
of	O
the	O
language	O
allow	O
automatic	B-General_Concept
garbage	I-General_Concept
collection	I-General_Concept
of	O
inaccessible	O
objects	O
,	O
most	O
implementations	O
do	O
not	O
support	O
it	O
by	O
default	O
,	O
as	O
it	O
would	O
cause	O
unpredictable	O
behaviour	O
in	O
real-time	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
Ada	B-Language
does	O
support	O
a	O
limited	O
form	O
of	O
region-based	B-General_Concept
memory	I-General_Concept
management	I-General_Concept
;	O
also	O
,	O
creative	O
use	O
of	O
storage	O
pools	O
can	O
provide	O
for	O
a	O
limited	O
form	O
of	O
automatic	B-General_Concept
garbage	I-General_Concept
collection	I-General_Concept
,	O
since	O
destroying	O
a	O
storage	O
pool	O
also	O
destroys	O
all	O
the	O
objects	O
in	O
the	O
pool	O
.	O
</s>
<s>
A	O
double-dash	O
("--"	O
)	O
,	O
resembling	O
an	O
em	O
dash	B-Protocol
,	O
denotes	O
comment	O
text	O
.	O
</s>
<s>
Unlike	O
most	O
ISO	O
standards	O
,	O
the	O
Ada	B-Language
language	I-Language
definition	O
(	O
known	O
as	O
the	O
Ada	B-Language
Reference	O
Manual	O
or	O
ARM	O
,	O
or	O
sometimes	O
the	O
Language	O
Reference	O
Manual	O
or	O
LRM	O
)	O
is	O
free	O
content	O
.	O
</s>
<s>
Thus	O
,	O
it	O
is	O
a	O
common	O
reference	O
for	O
Ada	B-Language
programmers	O
,	O
not	O
only	O
programmers	O
implementing	O
Ada	B-Language
compilers	B-Language
.	O
</s>
<s>
One	O
notable	O
free	B-Application
software	I-Application
tool	O
that	O
is	O
used	O
by	O
many	O
Ada	B-Language
programmers	O
to	O
aid	O
them	O
in	O
writing	O
Ada	B-Language
source	O
code	O
is	O
the	O
GNAT	B-Application
Programming	I-Application
Studio	I-Application
,	O
and	O
GNAT	B-Language
which	O
is	O
part	O
of	O
the	O
GNU	B-Application
Compiler	I-Application
Collection	I-Application
.	O
</s>
<s>
In	O
the	O
1970s	O
the	O
US	O
Department	O
of	O
Defense	O
(	O
DoD	O
)	O
became	O
concerned	O
by	O
the	O
number	O
of	O
different	O
programming	O
languages	O
being	O
used	O
for	O
its	O
embedded	B-Architecture
computer	I-Architecture
system	I-Architecture
projects	O
,	O
many	O
of	O
which	O
were	O
obsolete	O
or	O
hardware-dependent	O
,	O
and	O
none	O
of	O
which	O
supported	O
safe	B-Language
modular	B-Architecture
programming	I-Architecture
.	O
</s>
<s>
In	O
1975	O
,	O
a	O
working	O
group	O
,	O
the	O
High	B-Language
Order	I-Language
Language	I-Language
Working	I-Language
Group	I-Language
(	O
HOLWG	B-Language
)	O
,	O
was	O
formed	O
with	O
the	O
intent	O
to	O
reduce	O
this	O
number	O
by	O
finding	O
or	O
creating	O
a	O
programming	O
language	O
generally	O
suitable	O
for	O
the	O
department	O
's	O
and	O
the	O
UK	O
Ministry	O
of	O
Defence	O
's	O
requirements	O
.	O
</s>
<s>
After	O
many	O
iterations	O
beginning	O
with	O
an	O
original	O
straw	O
man	O
proposal	O
the	O
eventual	O
programming	O
language	O
was	O
named	O
Ada	B-Language
.	O
</s>
<s>
The	O
total	O
number	O
of	O
high-level	B-Language
programming	I-Language
languages	I-Language
in	O
use	O
for	O
such	O
projects	O
fell	O
from	O
over	O
450	O
in	O
1983	O
to	O
37	O
by	O
1996	O
.	O
</s>
<s>
HOLWG	B-Language
crafted	O
the	O
Steelman	B-Language
language	I-Language
requirements	I-Language
,	O
a	O
series	O
of	O
documents	O
stating	O
the	O
requirements	O
they	O
felt	O
a	O
programming	O
language	O
should	O
satisfy	O
.	O
</s>
<s>
In	O
May	O
1979	O
,	O
the	O
Green	O
proposal	O
,	O
designed	O
by	O
Jean	O
Ichbiah	O
at	O
Honeywell	O
,	O
was	O
chosen	O
and	O
given	O
the	O
name	O
Ada	B-Language
—	O
after	O
Augusta	B-General_Concept
Ada	I-General_Concept
,	I-General_Concept
Countess	I-General_Concept
of	I-General_Concept
Lovelace	I-General_Concept
.	O
</s>
<s>
This	O
proposal	O
was	O
influenced	O
by	O
the	O
language	O
LIS	B-General_Concept
that	O
Ichbiah	O
and	O
his	O
group	O
had	O
developed	O
in	O
the	O
1970s	O
.	O
</s>
<s>
The	O
preliminary	O
Ada	B-Language
reference	O
manual	O
was	O
published	O
in	O
ACM	O
SIGPLAN	O
Notices	O
in	O
June	O
1979	O
.	O
</s>
<s>
The	O
Military	O
Standard	O
reference	O
manual	O
was	O
approved	O
on	O
December	O
10	O
,	O
1980	O
(	O
Ada	B-General_Concept
Lovelace	I-General_Concept
's	O
birthday	O
)	O
,	O
and	O
given	O
the	O
number	O
MIL-STD-1815	B-Language
in	O
honor	O
of	O
Ada	B-General_Concept
Lovelace	I-General_Concept
's	O
birth	O
year	O
.	O
</s>
<s>
In	O
1981	O
,	O
C	O
.	O
A	O
.	O
R	O
.	O
Hoare	O
took	O
advantage	O
of	O
his	O
Turing	O
Award	O
speech	O
to	O
criticize	O
Ada	B-Language
for	O
being	O
overly	O
complex	O
and	O
hence	O
unreliable	O
,	O
but	O
subsequently	O
seemed	O
to	O
recant	O
in	O
the	O
foreword	O
he	O
wrote	O
for	O
an	O
Ada	B-Language
textbook	O
.	O
</s>
<s>
Ada	B-Language
attracted	O
much	O
attention	O
from	O
the	O
programming	O
community	O
as	O
a	O
whole	O
during	O
its	O
early	O
days	O
.	O
</s>
<s>
Ichbiah	O
publicly	O
stated	O
that	O
within	O
ten	O
years	O
,	O
only	O
two	O
programming	O
languages	O
would	O
remain	O
:	O
Ada	B-Language
and	O
Lisp	B-Language
.	O
</s>
<s>
Early	O
Ada	B-Language
compilers	B-Language
struggled	O
to	O
implement	O
the	O
large	O
,	O
complex	O
language	O
,	O
and	O
both	O
compile-time	B-Application
and	O
run-time	B-Device
performance	O
tended	O
to	O
be	O
slow	O
and	O
tools	O
primitive	O
.	O
</s>
<s>
Compiler	B-Language
vendors	O
expended	O
most	O
of	O
their	O
efforts	O
in	O
passing	O
the	O
massive	O
,	O
language-conformance-testing	O
,	O
government-required	O
Ada	B-Language
Compiler	I-Language
Validation	I-Language
Capability	I-Language
(	O
ACVC	B-Language
)	O
validation	O
suite	O
that	O
was	O
required	O
in	O
another	O
novel	O
feature	O
of	O
the	O
Ada	B-Language
language	I-Language
effort	O
.	O
</s>
<s>
The	O
Jargon	O
File	O
,	O
a	O
dictionary	O
of	O
computer	O
hacker	O
slang	O
originating	O
in	O
1975	O
–	O
1983	O
,	O
notes	O
in	O
an	O
entry	O
on	O
Ada	B-Language
that	O
"	O
it	O
is	O
precisely	O
what	O
one	O
might	O
expect	O
given	O
that	O
kind	O
of	O
endorsement	O
by	O
fiat	O
;	O
designed	O
by	O
committee	O
...	O
difficult	O
to	O
use	O
,	O
and	O
overall	O
a	O
disastrous	O
,	O
multi-billion-dollar	O
boondoggle	O
...	O
Ada	B-General_Concept
Lovelace	I-General_Concept
...	O
would	O
almost	O
certainly	O
blanch	O
at	O
the	O
use	O
her	O
name	O
has	O
been	O
latterly	O
put	O
to	O
;	O
the	O
kindest	O
thing	O
that	O
has	O
been	O
said	O
about	O
it	O
is	O
that	O
there	O
is	O
probably	O
a	O
good	O
small	O
language	O
screaming	O
to	O
get	O
out	O
from	O
inside	O
its	O
vast	O
,	O
elephantine	O
bulk.	O
"	O
</s>
<s>
The	O
first	O
validated	O
Ada	B-Language
implementation	O
was	O
the	O
NYU	O
Ada/Ed	O
translator	O
,	O
certified	O
on	O
April	O
11	O
,	O
1983	O
.	O
</s>
<s>
NYU	O
Ada/Ed	O
is	O
implemented	O
in	O
the	O
high-level	O
set	O
language	O
SETL	B-Language
.	O
</s>
<s>
Several	O
commercial	O
companies	O
began	O
offering	O
Ada	B-Language
compilers	B-Language
and	O
associated	O
development	O
tools	O
,	O
including	O
Alsys	O
,	O
TeleSoft	O
,	O
DDC-I	O
,	O
Advanced	O
Computer	O
Techniques	O
,	O
Tartan	O
Laboratories	O
,	O
Irvine	O
Compiler	B-Language
,	O
TLD	O
Systems	O
,	O
and	O
Verdix	O
.	O
</s>
<s>
Computer	O
manufacturers	O
who	O
had	O
a	O
significant	O
business	O
in	O
the	O
defense	O
,	O
aerospace	O
,	O
or	O
related	O
industries	O
,	O
also	O
offered	O
Ada	B-Language
compilers	B-Language
and	O
tools	O
on	O
their	O
platforms	O
;	O
these	O
included	O
Concurrent	B-Operating_System
Computer	O
Corporation	O
,	O
Cray	O
Research	O
,	O
Inc.	O
,	O
Harris	O
Computer	O
Systems	O
,	O
and	O
Siemens	O
Nixdorf	O
Informationssysteme	O
AG	O
.	O
</s>
<s>
In	O
1991	O
,	O
the	O
US	O
Department	O
of	O
Defense	O
began	O
to	O
require	O
the	O
use	O
of	O
Ada	B-Language
(	O
the	O
Ada	B-Language
mandate	O
)	O
for	O
all	O
software	O
,	O
though	O
exceptions	O
to	O
this	O
rule	O
were	O
often	O
granted	O
.	O
</s>
<s>
The	O
Department	O
of	O
Defense	O
Ada	B-Language
mandate	O
was	O
effectively	O
removed	O
in	O
1997	O
,	O
as	O
the	O
DoD	O
began	O
to	O
embrace	O
commercial	O
off-the-shelf	O
(	O
COTS	O
)	O
technology	O
.	O
</s>
<s>
Similar	O
requirements	O
existed	O
in	O
other	O
NATO	O
countries	O
:	O
Ada	B-Language
was	O
required	O
for	O
NATO	O
systems	O
involving	O
command	O
and	O
control	O
and	O
other	O
functions	O
,	O
and	O
Ada	B-Language
was	O
the	O
mandated	O
or	O
preferred	O
language	O
for	O
defense-related	O
applications	O
in	O
countries	O
such	O
as	O
Sweden	O
,	O
Germany	O
,	O
and	O
Canada	O
.	O
</s>
<s>
By	O
the	O
late	O
1980s	O
and	O
early	O
1990s	O
,	O
Ada	B-Language
compilers	B-Language
had	O
improved	O
in	O
performance	O
,	O
but	O
there	O
were	O
still	O
barriers	O
to	O
fully	O
exploiting	O
Ada	B-Language
's	O
abilities	O
,	O
including	O
a	O
tasking	O
model	O
that	O
was	O
different	O
from	O
what	O
most	O
real-time	B-General_Concept
programmers	O
were	O
used	O
to	O
.	O
</s>
<s>
Because	O
of	O
Ada	B-Language
's	O
safety-critical	B-Application
support	O
features	O
,	O
it	O
is	O
now	O
used	O
not	O
only	O
for	O
military	O
applications	O
,	O
but	O
also	O
in	O
commercial	O
projects	O
where	O
a	O
software	B-Error_Name
bug	I-Error_Name
can	O
have	O
severe	O
consequences	O
,	O
e.g.	O
,	O
avionics	O
and	O
air	B-Application
traffic	I-Application
control	I-Application
,	O
commercial	O
rockets	O
such	O
as	O
the	O
Ariane	O
4	O
and	O
5	O
,	O
satellites	B-Application
and	O
other	O
space	O
systems	O
,	O
railway	O
transport	O
and	O
banking	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
Airplane	B-Device
Information	I-Device
Management	I-Device
System	I-Device
,	O
the	O
fly-by-wire	O
system	O
software	O
in	O
the	O
Boeing	O
777	O
,	O
was	O
written	O
in	O
Ada	B-Language
.	O
</s>
<s>
Developed	O
by	O
Honeywell	O
Air	O
Transport	O
Systems	O
in	O
collaboration	O
with	O
consultants	O
from	O
DDC-I	O
,	O
it	O
became	O
arguably	O
the	O
best-known	O
of	O
any	O
Ada	B-Language
project	O
,	O
civilian	O
or	O
military	O
.	O
</s>
<s>
The	O
Canadian	O
Automated	O
Air	B-Application
Traffic	I-Application
System	O
was	O
written	O
in	O
1	O
million	O
lines	O
of	O
Ada	B-Language
(	O
SLOC	O
count	O
)	O
.	O
</s>
<s>
It	O
featured	O
advanced	O
distributed	B-Architecture
processing	I-Architecture
,	O
a	O
distributed	B-Architecture
Ada	B-Language
database	O
,	O
and	O
object-oriented	B-Language
design	O
.	O
</s>
<s>
Ada	B-Language
is	O
also	O
used	O
in	O
other	O
air	B-Application
traffic	I-Application
systems	O
,	O
e.g.	O
,	O
the	O
UK	O
's	O
next-generation	O
Interim	O
Future	O
Area	O
Control	O
Tools	O
Support	O
(	O
)	O
air	B-Application
traffic	I-Application
control	I-Application
system	I-Application
is	O
designed	O
and	O
implemented	O
using	O
SPARK	B-Language
Ada	B-Language
.	O
</s>
<s>
Preliminary	O
Ada	B-Language
can	O
be	O
found	O
in	O
.	O
</s>
<s>
Ada	B-Language
was	O
first	O
published	O
in	O
1980	O
as	O
an	O
ANSI	O
standard	O
ANSI/MIL	O
-STD	O
1815	O
.	O
</s>
<s>
This	O
version	O
of	O
the	O
language	O
is	O
commonly	O
known	O
as	O
Ada	B-Language
83	O
,	O
from	O
the	O
date	O
of	O
its	O
adoption	O
by	O
ANSI	O
,	O
but	O
is	O
sometimes	O
referred	O
to	O
also	O
as	O
Ada	B-Language
87	O
,	O
from	O
the	O
date	O
of	O
its	O
adoption	O
by	O
ISO	O
.	O
</s>
<s>
Ada	B-Language
95	O
,	O
the	O
joint	O
ISO/IEC/ANSI	O
standard	O
(	O
see	O
)	O
was	O
published	O
in	O
February	O
1995	O
,	O
making	O
it	O
the	O
first	O
ISO	O
standard	O
object-oriented	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
To	O
help	O
with	O
the	O
standard	O
revision	O
and	O
future	O
acceptance	O
,	O
the	O
US	O
Air	O
Force	O
funded	O
the	O
development	O
of	O
the	O
GNAT	B-Language
Compiler	I-Language
.	O
</s>
<s>
Presently	O
,	O
the	O
GNAT	B-Language
Compiler	I-Language
is	O
part	O
of	O
the	O
GNU	B-Application
Compiler	I-Application
Collection	I-Application
.	O
</s>
<s>
Work	O
has	O
continued	O
on	O
improving	O
and	O
updating	O
the	O
technical	O
content	O
of	O
the	O
Ada	B-Language
language	I-Language
.	O
</s>
<s>
A	O
Technical	O
Corrigendum	O
to	O
Ada	B-Language
95	O
was	O
published	O
in	O
October	O
2001	O
,	O
(	O
see	O
)	O
,	O
and	O
a	O
major	O
Amendment	O
,	O
(	O
see	O
)	O
was	O
published	O
on	O
March	O
9	O
,	O
2007	O
,	O
commonly	O
known	O
as	O
Ada	B-Language
2005	O
because	O
work	O
on	O
the	O
new	O
standard	O
was	O
finished	O
that	O
year	O
.	O
</s>
<s>
At	O
the	O
Ada-Europe	O
2012	O
conference	O
in	O
Stockholm	O
,	O
the	O
Ada	B-Language
Resource	O
Association	O
(	O
ARA	O
)	O
and	O
Ada-Europe	O
announced	O
the	O
completion	O
of	O
the	O
design	O
of	O
the	O
latest	O
version	O
of	O
the	O
Ada	B-Language
language	I-Language
and	O
the	O
submission	O
of	O
the	O
reference	O
manual	O
to	O
the	O
ISO/IEC	O
JTC	O
1/SC	O
22/WG	O
9	O
of	O
the	O
International	O
Organization	O
for	O
Standardization	O
(	O
ISO	O
)	O
and	O
the	O
International	O
Electrotechnical	O
Commission	O
(	O
IEC	O
)	O
for	O
approval	O
.	O
</s>
<s>
(	O
see	O
)	O
was	O
published	O
in	O
December	O
2012	O
,	O
known	O
as	O
Ada	B-Language
2012	O
.	O
</s>
<s>
Despite	O
the	O
names	O
Ada	B-Language
83	I-Language
,	O
95	O
etc.	O
,	O
legally	O
there	O
is	O
only	O
one	O
Ada	B-Language
standard	O
,	O
the	O
one	O
of	O
the	O
last	O
ISO/IEC	O
standard	O
:	O
with	O
the	O
acceptance	O
of	O
a	O
new	O
standard	O
version	O
,	O
the	O
previous	O
one	O
becomes	O
withdrawn	O
.	O
</s>
<s>
Other	O
related	O
standards	O
include	O
ISO/IEC	O
8651-3:1988	O
Information	O
processing	O
systems	O
—	O
Computer	O
graphics	O
—	O
Graphical	O
Kernel	O
System	O
(	O
GKS	O
)	O
language	O
bindings	O
—	O
Part	O
3	O
:	O
Ada	B-Language
.	O
</s>
<s>
Ada	B-Language
is	O
an	O
ALGOL-like	B-Language
programming	O
language	O
featuring	O
control	O
structures	O
with	O
reserved	O
words	O
such	O
as	O
if	O
,	O
then	O
,	O
else	O
,	O
while	O
,	O
for	O
,	O
and	O
so	O
on	O
.	O
</s>
<s>
However	O
,	O
Ada	B-Language
also	O
has	O
many	O
data	O
structuring	O
facilities	O
and	O
other	O
abstractions	O
which	O
were	O
not	O
included	O
in	O
the	O
original	O
ALGOL	B-Language
60	I-Language
,	O
such	O
as	O
type	O
definitions	O
,	O
records	O
,	O
pointers	O
,	O
enumerations	B-Language
.	O
</s>
<s>
Such	O
constructs	O
were	O
in	O
part	O
inherited	O
from	O
or	O
inspired	O
by	O
Pascal	B-Application
.	O
</s>
<s>
Ada	B-Language
's	O
type	O
system	O
is	O
not	O
based	O
on	O
a	O
set	O
of	O
predefined	O
primitive	O
types	O
but	O
allows	O
users	O
to	O
declare	O
their	O
own	O
types	O
.	O
</s>
<s>
This	O
allows	O
the	O
compiler	B-Language
to	O
determine	O
a	O
suitable	O
memory	O
size	O
for	O
the	O
type	O
,	O
and	O
to	O
check	O
for	O
violations	O
of	O
the	O
type	O
definition	O
at	O
compile	B-Application
time	I-Application
and	O
run	B-Library
time	I-Library
(	O
i.e.	O
,	O
range	O
violations	O
,	O
buffer	B-General_Concept
overruns	I-General_Concept
,	O
type	O
consistency	O
,	O
etc	O
.	O
)	O
.	O
</s>
<s>
Ada	B-Language
supports	O
numerical	O
types	O
defined	O
by	O
a	O
range	O
,	O
modulo	O
types	O
,	O
aggregate	O
types	O
(	O
records	O
and	O
arrays	O
)	O
,	O
and	O
enumeration	B-Language
types	O
.	O
</s>
<s>
Ada	B-Language
95	I-Language
adds	O
further	O
features	O
for	O
object-oriented	B-Language
extension	O
of	O
types	O
.	O
</s>
<s>
Ada	B-Language
is	O
a	O
structured	B-Language
programming	I-Language
language	O
,	O
meaning	O
that	O
the	O
flow	O
of	O
control	O
is	O
structured	B-Language
into	O
standard	O
statements	O
.	O
</s>
<s>
Among	O
the	O
parts	O
of	O
an	O
Ada	B-Language
program	O
are	O
packages	O
,	O
procedures	O
and	O
functions	O
.	O
</s>
<s>
Ada	B-Language
has	O
language	O
support	O
for	O
task-based	O
concurrency	B-Architecture
.	O
</s>
<s>
The	O
fundamental	O
concurrent	B-Operating_System
unit	O
in	O
Ada	B-Language
is	O
a	O
task	O
,	O
which	O
is	O
a	O
built-in	O
limited	O
type	O
.	O
</s>
<s>
Tasks	B-General_Concept
are	O
specified	O
in	O
two	O
parts	O
–	O
the	O
task	O
declaration	O
defines	O
the	O
task	O
interface	O
(	O
similar	O
to	O
a	O
type	O
declaration	O
)	O
,	O
the	O
task	O
body	O
specifies	O
the	O
implementation	O
of	O
the	O
task	O
.	O
</s>
<s>
Depending	O
on	O
the	O
implementation	O
,	O
Ada	B-Language
tasks	B-General_Concept
are	O
either	O
mapped	O
to	O
operating	O
system	O
threads	O
or	O
processes	O
,	O
or	O
are	O
scheduled	O
internally	O
by	O
the	O
Ada	B-Language
runtime	B-Library
.	O
</s>
<s>
Tasks	B-General_Concept
can	O
have	O
entries	O
for	O
synchronisation	O
(	O
a	O
form	O
of	O
synchronous	B-Architecture
message	I-Architecture
passing	I-Architecture
)	O
.	O
</s>
<s>
Task	O
entries	O
can	O
have	O
parameters	O
similar	O
to	O
procedures	O
,	O
allowing	O
tasks	B-General_Concept
to	O
synchronously	O
exchange	O
data	O
.	O
</s>
<s>
In	O
conjunction	O
with	O
select	O
statements	O
it	O
is	O
possible	O
to	O
define	O
guards	O
on	O
accept	O
statements	O
(	O
similar	O
to	O
Dijkstra	O
's	O
guarded	B-Application
commands	I-Application
)	O
.	O
</s>
<s>
Ada	B-Language
also	O
offers	O
protected	O
objects	O
for	O
mutual	B-Operating_System
exclusion	I-Operating_System
.	O
</s>
<s>
Protected	O
objects	O
combine	O
the	O
data	O
encapsulation	O
and	O
safe	B-Language
mutual	B-Operating_System
exclusion	I-Operating_System
from	O
monitors	O
,	O
and	O
entry	O
guards	O
from	O
conditional	O
critical	O
regions	O
.	O
</s>
<s>
The	O
main	O
advantage	O
over	O
classical	O
monitors	O
is	O
that	O
conditional	O
variables	O
are	O
not	O
required	O
for	O
signaling	O
,	O
avoiding	O
potential	O
deadlocks	B-Operating_System
due	O
to	O
incorrect	O
locking	O
semantics	O
.	O
</s>
<s>
Like	O
tasks	B-General_Concept
,	O
the	O
protected	O
object	O
is	O
a	O
built-in	O
limited	O
type	O
,	O
and	O
it	O
also	O
has	O
a	O
declaration	O
part	O
and	O
a	O
body	O
.	O
</s>
<s>
Blocked	O
tasks	B-General_Concept
are	O
queued	O
on	O
the	O
protected	O
object	O
ordered	O
by	O
time	O
of	O
arrival	O
.	O
</s>
<s>
The	O
select	O
statement	O
in	O
Ada	B-Language
can	O
be	O
used	O
to	O
implement	O
non-blocking	O
entry	O
calls	O
and	O
accepts	O
,	O
non-deterministic	O
selection	O
of	O
entries	O
(	O
also	O
with	O
guards	O
)	O
,	O
time-outs	O
and	O
aborts	O
.	O
</s>
<s>
The	O
following	O
example	O
illustrates	O
some	O
concepts	O
of	O
concurrent	B-Architecture
programming	I-Architecture
in	O
Ada	B-Language
.	O
</s>
<s>
A	O
pragma	O
is	O
a	O
compiler	B-Language
directive	O
that	O
conveys	O
information	O
to	O
the	O
compiler	B-Language
to	O
allow	O
specific	O
manipulating	O
of	O
compiled	B-Language
output	O
.	O
</s>
<s>
Examples	O
of	O
common	O
usage	O
of	O
compiler	B-Language
pragmas	O
would	O
be	O
to	O
disable	O
certain	O
features	O
,	O
such	O
as	O
run-time	B-Device
type	O
checking	O
or	O
array	B-Application
subscript	O
boundary	O
checking	O
,	O
or	O
to	O
instruct	O
the	O
compiler	B-Language
to	O
insert	O
object	O
code	O
instead	O
of	O
a	O
function	O
call	O
(	O
as	O
C/C	O
++	O
does	O
with	O
inline	O
functions	O
)	O
.	O
</s>
