<s>
Simula	B-Language
is	I-Language
the	O
name	O
of	O
two	O
simulation	B-Language
programming	O
languages	O
,	O
Simula	B-Language
I	I-Language
and	O
Simula	B-Language
67	I-Language
,	O
developed	O
in	O
the	O
1960s	O
at	O
the	O
Norwegian	O
Computing	O
Center	O
in	O
Oslo	O
,	O
by	O
Ole-Johan	O
Dahl	O
and	O
Kristen	O
Nygaard	O
.	O
</s>
<s>
Syntactically	O
,	O
it	O
is	O
an	O
approximate	O
superset	O
of	O
ALGOL	B-Language
60	I-Language
,	O
and	O
was	O
also	O
influenced	O
by	O
the	O
design	O
of	O
Simscript	B-Language
.	O
</s>
<s>
Simula	B-Language
67	I-Language
introduced	O
objects	O
,	O
classes	O
,	O
inheritance	B-Language
and	O
subclasses	O
,	O
virtual	B-Application
procedures	I-Application
,	O
coroutines	B-Architecture
,	O
and	O
discrete	B-General_Concept
event	I-General_Concept
simulation	I-General_Concept
,	O
and	O
featured	O
garbage	B-General_Concept
collection	I-General_Concept
.	O
</s>
<s>
Other	O
forms	O
of	O
subtyping	O
(	O
besides	O
inheriting	O
subclasses	O
)	O
were	O
introduced	O
in	O
Simula	B-Language
derivatives	O
.	O
</s>
<s>
Simula	B-Language
is	I-Language
considered	O
the	O
first	O
object-oriented	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
As	O
its	O
name	O
suggests	O
,	O
the	O
first	O
Simula	B-Language
version	O
by	O
1962	O
was	O
designed	O
for	O
doing	O
simulations	O
;	O
Simula	B-Language
67	I-Language
though	O
was	O
designed	O
to	O
be	O
a	O
general-purpose	O
programming	O
language	O
and	O
provided	O
the	O
framework	O
for	O
many	O
of	O
the	O
features	O
of	O
object-oriented	B-Language
languages	I-Language
today	O
.	O
</s>
<s>
Simula	B-Language
has	O
been	O
used	O
in	O
a	O
wide	O
range	O
of	O
applications	O
such	O
as	O
simulating	O
very-large-scale	O
integration	O
(	O
VLSI	O
)	O
designs	O
,	O
process	O
modeling	O
,	O
communication	O
protocols	O
,	O
algorithms	O
,	O
and	O
other	O
applications	O
such	O
as	O
typesetting	O
,	O
computer	O
graphics	O
,	O
and	O
education	O
.	O
</s>
<s>
The	O
influence	O
of	O
Simula	B-Language
is	I-Language
often	O
understated	O
,	O
and	O
Simula-type	O
objects	O
are	O
reimplemented	O
in	O
C++	B-Language
,	O
Object	B-Language
Pascal	I-Language
,	O
Java	B-Language
,	O
C#	B-Application
,	O
and	O
many	O
other	O
languages	O
.	O
</s>
<s>
Computer	O
scientists	O
such	O
as	O
Bjarne	O
Stroustrup	O
,	O
creator	O
of	O
C++	B-Language
,	O
and	O
James	O
Gosling	O
,	O
creator	O
of	O
Java	B-Language
,	O
have	O
acknowledged	O
Simula	B-Language
as	O
a	O
major	O
influence	O
.	O
</s>
<s>
Kristen	O
Nygaard	O
started	O
writing	O
computer	O
simulation	B-Language
programs	O
in	O
1957	O
.	O
</s>
<s>
To	O
go	O
further	O
with	O
his	O
ideas	O
on	O
a	O
formal	O
computer	B-Language
language	I-Language
for	O
describing	O
a	O
system	O
,	O
Nygaard	O
realized	O
that	O
he	O
needed	O
someone	O
with	O
more	O
computer	B-General_Concept
programming	I-General_Concept
skills	O
than	O
he	O
had	O
.	O
</s>
<s>
The	O
decision	O
of	O
linking	O
the	O
language	O
up	O
to	O
ALGOL	B-Language
60	I-Language
was	O
made	O
shortly	O
after	O
.	O
</s>
<s>
By	O
May	O
1962	O
,	O
the	O
main	O
concepts	O
for	O
a	O
simulation	B-Language
language	I-Language
were	O
set	O
.	O
</s>
<s>
SIMULA	B-Language
I	I-Language
was	O
born	O
,	O
a	O
special	O
purpose	O
programming	O
language	O
for	O
simulating	O
discrete	O
event	O
systems	O
.	O
</s>
<s>
At	O
that	O
visit	O
,	O
Nygaard	O
presented	O
the	O
ideas	O
of	O
Simula	B-Language
to	O
Robert	O
Bemer	O
,	O
the	O
director	O
of	O
systems	O
programming	O
at	O
Univac	O
.	O
</s>
<s>
Bemer	O
was	O
a	O
great	O
ALGOL	B-Language
fan	O
and	O
found	O
the	O
Simula	B-Language
project	O
compelling	O
.	O
</s>
<s>
He	O
invited	O
Nygaard	O
,	O
who	O
presented	O
the	O
paper	O
"	O
SIMULA	B-Language
–	O
An	O
Extension	O
of	O
ALGOL	B-Language
to	O
the	O
Description	O
of	O
Discrete-Event	O
Networks	O
"	O
.	O
</s>
<s>
The	O
Norwegian	O
Computing	O
Center	O
got	O
a	O
UNIVAC	O
1107	O
in	O
August	O
1963	O
at	O
a	O
considerable	O
discount	O
,	O
on	O
which	O
Dahl	O
implemented	O
the	O
SIMULA	B-Language
I	I-Language
under	O
contract	O
with	O
UNIVAC	O
.	O
</s>
<s>
The	O
implementation	O
was	O
based	O
on	O
the	O
UNIVAC	O
ALGOL	B-Language
60	I-Language
compiler	O
.	O
</s>
<s>
SIMULA	B-Language
I	I-Language
was	O
fully	O
operational	O
on	O
the	O
UNIVAC	O
1107	O
by	O
January	O
1965	O
.	O
</s>
<s>
In	O
the	O
following	O
few	O
years	O
,	O
Dahl	O
and	O
Nygaard	O
spent	O
a	O
lot	O
of	O
time	O
teaching	O
Simula	B-Language
.	O
</s>
<s>
Simula	B-Language
spread	O
to	O
several	O
countries	O
around	O
the	O
world	O
and	O
SIMULA	B-Language
I	I-Language
was	O
later	O
implemented	O
on	O
other	O
computers	O
including	O
the	O
Burroughs	B-Device
B5500	I-Device
and	O
the	O
Russian	O
Ural-16	O
.	O
</s>
<s>
Dahl	O
and	O
Nygaard	O
presented	O
their	O
paper	O
on	O
Class	O
and	O
Subclass	O
declarations	O
at	O
the	O
IFIP	O
Working	O
Conference	O
on	O
simulation	B-Language
languages	I-Language
in	O
Oslo	O
,	O
May	O
1967	O
.	O
</s>
<s>
This	O
paper	O
became	O
the	O
first	O
formal	O
definition	O
of	O
Simula	B-Language
67	I-Language
.	O
</s>
<s>
Simula	B-Language
67	I-Language
was	O
formally	O
standardized	O
on	O
the	O
first	O
meeting	O
of	O
the	O
Simula	B-Language
Standards	O
Group	O
(	O
SSG	O
)	O
in	O
February	O
1968	O
.	O
</s>
<s>
Simula	B-Language
was	O
influential	O
in	O
the	O
development	O
of	O
Smalltalk	B-Application
and	O
later	O
object-oriented	B-Language
programming	I-Language
languages	I-Language
.	O
</s>
<s>
It	O
also	O
helped	O
inspire	O
the	O
actor	B-Application
model	I-Application
of	O
concurrent	O
computation	O
although	O
Simula	B-Language
only	O
supports	O
coroutines	B-Architecture
and	O
not	O
true	O
concurrency	B-Operating_System
.	O
</s>
<s>
In	O
the	O
late	O
sixties	O
and	O
the	O
early	O
seventies	O
,	O
there	O
were	O
four	O
main	O
implementations	O
of	O
Simula	B-Language
:	O
</s>
<s>
The	O
TOPS-10	B-Operating_System
implemented	O
the	O
concept	O
of	O
public	O
,	O
protected	O
,	O
and	O
private	O
member	O
variables	O
and	O
procedures	O
,	O
that	O
later	O
was	O
integrated	O
into	O
Simula	B-Language
87	O
.	O
</s>
<s>
Simula	B-Language
87	O
is	O
the	O
latest	O
standard	O
and	O
is	O
ported	O
to	O
a	O
wide	O
range	O
of	O
platforms	O
.	O
</s>
<s>
In	O
November	O
2001	O
,	O
Dahl	O
and	O
Nygaard	O
were	O
awarded	O
the	O
IEEE	O
John	O
von	O
Neumann	O
Medal	O
by	O
the	O
Institute	O
of	O
Electrical	O
and	O
Electronics	O
Engineers	O
"	O
For	O
the	O
introduction	O
of	O
the	O
concepts	O
underlying	O
object-oriented	B-Language
programming	I-Language
through	O
the	O
design	O
and	O
implementation	O
of	O
SIMULA	B-Language
67	I-Language
"	O
.	O
</s>
<s>
In	O
April	O
2002	O
,	O
they	O
received	O
the	O
2001	O
A	O
.	O
M	O
.	O
Turing	O
Award	O
by	O
the	O
Association	O
for	O
Computing	O
Machinery	O
(	O
ACM	O
)	O
,	O
with	O
the	O
citation	O
:	O
"	O
For	O
ideas	O
fundamental	O
to	O
the	O
emergence	O
of	O
object	B-Language
oriented	I-Language
programming	I-Language
,	O
through	O
their	O
design	O
of	O
the	O
programming	O
languages	O
Simula	B-Language
I	I-Language
and	O
Simula	O
67.	O
"	O
</s>
<s>
Simula	B-Language
Research	O
Laboratory	O
is	O
a	O
research	O
institute	O
named	O
after	O
the	O
Simula	B-Language
language	O
,	O
and	O
Nygaard	O
held	O
a	O
part-time	O
position	O
there	O
from	O
the	O
opening	O
in	O
2001	O
.	O
</s>
<s>
The	O
new	O
Computer	O
Science	O
building	O
at	O
the	O
University	O
of	O
Oslo	O
is	O
named	O
Ole	O
Johan	O
Dahl	O
's	O
House	O
,	O
in	O
Dahl	O
's	O
honour	O
,	O
and	O
the	O
main	O
auditorium	O
is	O
named	O
Simula	B-Language
.	O
</s>
<s>
The	O
empty	O
computer	B-Operating_System
file	I-Operating_System
is	O
the	O
minimal	O
program	B-Application
in	O
Simula	B-Language
,	O
measured	O
by	O
the	O
size	O
of	O
the	O
source	O
code	O
.	O
</s>
<s>
However	O
,	O
the	O
minimal	O
program	B-Application
is	O
more	O
conveniently	O
represented	O
as	O
an	O
empty	O
block	O
:	O
</s>
<s>
The	O
language	O
lacks	O
any	O
return	B-Language
value	I-Language
from	O
the	O
program	B-Application
.	O
</s>
<s>
An	O
example	O
of	O
a	O
Hello	O
world	O
program	B-Application
in	O
Simula	B-Language
:	O
</s>
<s>
Simula	B-Language
is	I-Language
case-insensitive	O
.	O
</s>
<s>
A	O
more	O
realistic	O
example	O
with	O
use	O
of	O
classes	O
,	O
subclasses	O
and	O
virtual	B-Application
procedures	I-Application
:	O
</s>
<s>
Main	O
program	B-Application
;	O
</s>
<s>
There	O
is	O
one	O
virtual	B-Application
procedure	I-Application
with	O
two	O
implementations	O
.	O
</s>
<s>
The	O
execution	O
starts	O
by	O
executing	O
the	O
main	O
program	B-Application
.	O
</s>
<s>
Simula	B-Language
lacks	O
the	O
concept	O
of	O
abstract	O
classes	O
,	O
since	O
classes	O
with	O
pure	O
virtual	B-Application
procedures	I-Application
can	O
be	O
instantiated	O
.	O
</s>
<s>
Calling	O
a	O
pure	O
virtual	B-Application
procedure	I-Application
will	O
however	O
produce	O
a	O
run-time	B-Library
error	I-Library
.	O
</s>
<s>
Simula	B-Language
supports	O
call	O
by	O
name	O
so	O
the	O
Jensen	O
's	O
Device	O
can	O
easily	O
be	O
implemented	O
.	O
</s>
<s>
However	O
,	O
the	O
default	O
transmission	O
mode	O
for	O
simple	O
parameter	O
is	O
call	O
by	O
value	O
,	O
contrary	O
to	O
ALGOL	B-Language
which	O
used	O
call	O
by	O
name	O
.	O
</s>
<s>
The	O
source	O
code	O
for	O
the	O
Jensen	O
's	O
Device	O
must	O
therefore	O
specify	O
call	O
by	O
name	O
for	O
the	O
parameters	O
when	O
compiled	O
by	O
a	O
Simula	B-Language
compiler	O
.	O
</s>
<s>
in	O
a	O
for	B-Language
loop	I-Language
.	O
</s>
<s>
Simula	B-Language
includes	O
a	O
simulation	B-Language
package	O
for	O
doing	O
discrete	B-General_Concept
event	I-General_Concept
simulations	I-General_Concept
.	O
</s>
<s>
This	O
simulation	B-Language
package	O
is	O
based	O
on	O
Simula	B-Language
's	O
object-oriented	B-Language
features	O
and	O
its	O
coroutine	B-Architecture
concept	O
.	O
</s>
<s>
A	O
simulation	B-Language
of	O
their	O
fitting	O
room	O
experience	O
is	O
as	O
follows	O
:	O
</s>
<s>
The	O
main	O
block	O
is	O
prefixed	O
with	O
Simulation	B-Language
for	O
enabling	O
simulation	B-Language
.	O
</s>
<s>
The	O
simulation	B-Language
package	O
can	O
be	O
used	O
on	O
any	O
block	O
and	O
simulations	O
can	O
even	O
be	O
nested	O
when	O
simulating	O
someone	O
doing	O
simulations	O
.	O
</s>
<s>
The	O
main	O
program	B-Application
creates	O
all	O
the	O
objects	O
and	O
activates	O
all	O
the	O
person	O
objects	O
to	O
put	O
them	O
into	O
the	O
event	O
queue	O
.	O
</s>
<s>
The	O
main	O
program	B-Application
holds	O
for	O
100	O
minutes	O
of	O
simulated	O
time	O
before	O
the	O
program	B-Application
terminates	O
.	O
</s>
