<s>
Fortran	O
(	O
;	O
formerly	O
FORTRAN	O
)	O
is	O
a	O
general-purpose	O
,	O
compiled	B-Language
imperative	B-Application
programming	I-Application
language	I-Application
that	O
is	O
especially	O
suited	O
to	O
numeric	B-General_Concept
computation	I-General_Concept
and	O
scientific	O
computing	O
.	O
</s>
<s>
It	O
has	O
been	O
in	O
use	O
for	O
over	O
six	O
decades	O
in	O
computationally	O
intensive	O
areas	O
such	O
as	O
numerical	B-General_Concept
weather	I-General_Concept
prediction	I-General_Concept
,	O
finite	B-Application
element	I-Application
analysis	I-Application
,	O
computational	O
fluid	O
dynamics	O
,	O
geophysics	O
,	O
computational	B-Algorithm
physics	I-Algorithm
,	O
crystallography	O
and	O
computational	O
chemistry	O
.	O
</s>
<s>
It	O
is	O
a	O
popular	O
language	O
for	O
high-performance	B-Architecture
computing	I-Architecture
and	O
is	O
used	O
for	O
programs	O
that	O
benchmark	O
and	O
rank	O
the	O
world	O
's	O
fastest	B-Operating_System
supercomputers	I-Operating_System
.	O
</s>
<s>
Fortran	O
's	O
design	O
was	O
the	O
basis	O
for	O
many	O
other	O
programming	O
languages	O
,	O
especially	O
BASIC	O
and	O
ALGOL	B-Language
.	O
</s>
<s>
Successive	O
versions	O
have	O
added	O
support	O
for	O
structured	B-Language
programming	I-Language
and	O
processing	O
of	O
character-based	O
data	O
(	O
FORTRAN	O
77	O
)	O
,	O
array	B-Application
programming	I-Application
,	O
modular	B-Architecture
programming	I-Architecture
and	O
generic	B-Language
programming	I-Language
(	O
Fortran	O
90	O
)	O
,	O
High	B-Language
Performance	I-Language
Fortran	I-Language
(	O
Fortran	O
95	O
)	O
,	O
object-oriented	B-Language
programming	I-Language
(	O
Fortran	O
2003	O
)	O
,	O
concurrent	B-Architecture
programming	I-Architecture
(	O
Fortran	O
2008	O
)	O
,	O
and	O
native	O
parallel	B-Operating_System
computing	I-Operating_System
capabilities	O
(	O
Coarray	B-Language
Fortran	I-Language
2008/2018	O
)	O
.	O
</s>
<s>
The	O
first	O
manual	B-Protocol
for	O
FORTRAN	O
describes	O
it	O
as	O
a	O
Formula	O
Translating	O
System	O
,	O
and	O
printed	O
the	O
name	O
with	O
small	O
caps	O
,	O
FORTRAN	O
.	O
</s>
<s>
In	O
late	O
1953	O
,	O
John	O
W	O
.	O
Backus	O
submitted	O
a	O
proposal	O
to	O
his	O
superiors	O
at	O
IBM	O
to	O
develop	O
a	O
more	O
practical	O
alternative	O
to	O
assembly	B-Language
language	I-Language
for	O
programming	O
their	O
IBM	B-Device
704	I-Device
mainframe	B-Architecture
computer	I-Architecture
.	O
</s>
<s>
Backus	O
 '	O
historic	O
FORTRAN	O
team	O
consisted	O
of	O
programmers	O
Richard	O
Goldberg	O
,	O
Sheldon	O
F	B-Language
.	O
Best	O
,	O
Harlan	O
Herrick	O
,	O
Peter	O
Sheridan	O
,	O
Roy	O
Nutt	O
,	O
Robert	O
Nelson	O
,	O
Irving	O
Ziller	O
,	O
Harold	O
Stern	O
,	O
Lois	O
Haibt	O
,	O
and	O
David	O
Sayre	O
.	O
</s>
<s>
The	O
first	O
manual	B-Protocol
for	O
FORTRAN	O
appeared	O
in	O
October	O
1956	O
,	O
with	O
the	O
first	O
FORTRAN	O
compiler	B-Language
delivered	O
in	O
April	O
1957	O
.	O
</s>
<s>
This	O
was	O
the	O
first	O
optimizing	B-Application
compiler	I-Application
,	O
because	O
customers	O
were	O
reluctant	O
to	O
use	O
a	O
high-level	B-Language
programming	I-Language
language	I-Language
unless	O
its	O
compiler	B-Language
could	O
generate	O
code	O
with	O
performance	O
approaching	O
that	O
of	O
hand-coded	O
assembly	B-Language
language	I-Language
.	O
</s>
<s>
I	O
did	O
n't	O
like	O
writing	O
programs	O
,	O
and	O
so	O
,	O
when	O
I	O
was	O
working	O
on	O
the	O
IBM	B-Device
701	I-Device
,	O
writing	O
programs	O
for	O
computing	O
missile	O
trajectories	O
,	O
I	O
started	O
work	O
on	O
a	O
programming	O
system	O
to	O
make	O
it	O
easier	O
to	O
write	O
programs.	O
"	O
</s>
<s>
The	O
language	O
was	O
widely	O
adopted	O
by	O
scientists	O
for	O
writing	O
numerically	B-General_Concept
intensive	O
programs	O
,	O
which	O
encouraged	O
compiler	B-Language
writers	O
to	O
produce	O
compilers	B-Language
that	O
could	O
generate	O
faster	O
and	O
more	O
efficient	O
code	O
.	O
</s>
<s>
By	O
1960	O
,	O
versions	O
of	O
FORTRAN	O
were	O
available	O
for	O
the	O
IBM	B-Device
709	I-Device
,	O
650	B-Device
,	O
1620	B-Device
,	O
and	O
7090	B-Device
computers	O
.	O
</s>
<s>
Significantly	O
,	O
the	O
increasing	O
popularity	O
of	O
FORTRAN	O
spurred	O
competing	O
computer	O
manufacturers	O
to	O
provide	O
FORTRAN	O
compilers	B-Language
for	O
their	O
machines	O
,	O
so	O
that	O
by	O
1963	O
over	O
40	O
FORTRAN	O
compilers	B-Language
existed	O
.	O
</s>
<s>
For	O
these	O
reasons	O
,	O
FORTRAN	O
is	O
considered	O
to	O
be	O
the	O
first	O
widely	O
used	O
cross-platform	B-Operating_System
programming	O
language	O
.	O
</s>
<s>
The	O
development	O
of	O
Fortran	O
paralleled	O
the	O
early	B-Application
evolution	I-Application
of	I-Application
compiler	I-Application
technology	I-Application
,	O
and	O
many	O
advances	O
in	O
the	O
theory	O
and	O
design	O
of	O
compilers	B-Language
were	O
specifically	O
motivated	O
by	O
the	O
need	O
to	O
generate	O
efficient	O
code	O
for	O
Fortran	O
programs	O
.	O
</s>
<s>
The	O
initial	O
release	O
of	O
FORTRAN	O
for	O
the	O
IBM	B-Device
704	I-Device
contained	O
32	O
statements	O
,	O
including	O
:	O
</s>
<s>
statement	O
(	O
for	O
providing	O
optimization	O
hints	O
to	O
the	O
compiler	B-Language
)	O
.	O
</s>
<s>
The	O
first	O
FORTRAN	O
compiler	B-Language
used	O
this	O
weighting	O
to	O
perform	O
at	O
compile	B-Language
time	O
a	O
Monte	B-Algorithm
Carlo	I-Algorithm
simulation	I-Algorithm
of	O
the	O
generated	O
code	O
,	O
the	O
results	O
of	O
which	O
were	O
used	O
to	O
optimize	O
the	O
placement	O
of	O
basic	B-Application
blocks	I-Application
in	O
memory	O
—	O
a	O
very	O
sophisticated	O
optimization	O
for	O
its	O
time	O
.	O
</s>
<s>
The	O
fundamental	O
unit	O
of	O
program	O
is	O
the	O
basic	B-Application
block	I-Application
;	O
a	O
basic	B-Application
block	I-Application
is	O
a	O
stretch	O
of	O
program	O
which	O
has	O
one	O
entry	O
point	O
and	O
one	O
exit	O
point	O
.	O
</s>
<s>
The	O
purpose	O
of	O
section	O
4	O
is	O
to	O
prepare	O
for	O
section	O
5	O
a	O
table	O
of	O
predecessors	O
(	O
PRED	O
table	O
)	O
which	O
enumerates	O
the	O
basic	B-Application
blocks	I-Application
and	O
lists	O
for	O
every	O
basic	B-Application
block	I-Application
each	O
of	O
the	O
basic	B-Application
blocks	I-Application
which	O
can	O
be	O
its	O
immediate	O
predecessor	O
in	O
flow	O
,	O
together	O
with	O
the	O
absolute	O
frequency	O
of	O
each	O
such	O
basic	B-Application
block	I-Application
link	O
.	O
</s>
<s>
The	O
first	O
FORTRAN	O
compiler	B-Language
reported	O
diagnostic	O
information	O
by	O
halting	O
the	O
program	O
when	O
an	O
error	O
was	O
found	O
and	O
outputting	O
an	O
error	O
code	O
on	O
its	O
console	O
.	O
</s>
<s>
That	O
code	O
could	O
be	O
looked	O
up	O
by	O
the	O
programmer	O
in	O
an	O
error	O
messages	O
table	O
in	O
the	O
operator	O
's	O
manual	B-Protocol
,	O
providing	O
them	O
with	O
a	O
brief	O
description	O
of	O
the	O
problem	O
.	O
</s>
<s>
Before	O
the	O
development	O
of	O
disk	O
files	O
,	O
text	O
editors	O
and	O
terminals	O
,	O
programs	O
were	O
most	O
often	O
entered	O
on	O
a	O
keypunch	B-Device
keyboard	O
onto	O
80-column	O
punched	B-Architecture
cards	I-Architecture
,	O
one	O
line	O
to	O
a	O
card	O
.	O
</s>
<s>
The	O
resulting	O
deck	O
of	O
cards	O
would	O
be	O
fed	O
into	O
a	O
card	B-Device
reader	I-Device
to	O
be	O
compiled	B-Language
.	O
</s>
<s>
Punched	B-Architecture
card	I-Architecture
codes	O
included	O
no	O
lower-case	O
letters	O
or	O
many	O
special	O
characters	O
,	O
and	O
special	O
versions	O
of	O
the	O
IBM	O
026	O
keypunch	B-Device
were	O
offered	O
that	O
would	O
correctly	O
print	O
the	O
re-purposed	O
special	O
characters	O
used	O
in	O
FORTRAN	O
.	O
</s>
<s>
Reflecting	O
punched	B-Architecture
card	I-Architecture
input	O
practice	O
,	O
Fortran	O
programs	O
were	O
originally	O
written	O
in	O
a	O
fixed-column	O
format	O
,	O
with	O
the	O
first	O
72	O
columns	O
read	O
into	O
twelve	O
36-bit	O
words	O
.	O
</s>
<s>
A	O
letter	O
"	O
C	B-Language
"	O
in	O
column	O
1	O
caused	O
the	O
entire	O
card	O
to	O
be	O
treated	O
as	O
a	O
comment	O
and	O
ignored	O
by	O
the	O
compiler	B-Language
.	O
</s>
<s>
73	O
to	O
80	O
were	O
ignored	O
(	O
the	O
IBM	B-Device
704	I-Device
's	O
card	B-Device
reader	I-Device
only	O
used	O
72	O
columns	O
)	O
.	O
</s>
<s>
Some	O
early	O
compilers	B-Language
,	O
e.g.	O
,	O
the	O
IBM	B-Device
650	I-Device
's	O
,	O
had	O
additional	O
restrictions	O
due	O
to	O
limitations	O
on	O
their	O
card	O
readers	O
.	O
</s>
<s>
Keypunches	B-Device
could	O
be	O
programmed	O
to	O
tab	O
to	O
column	O
7	O
and	O
skip	O
out	O
after	O
column	O
72	O
.	O
</s>
<s>
Later	O
compilers	B-Language
relaxed	O
most	O
fixed-format	O
restrictions	O
,	O
and	O
the	O
requirement	O
was	O
eliminated	O
in	O
the	O
Fortran	O
90	O
standard	O
.	O
</s>
<s>
Hollerith	B-Language
strings	I-Language
,	O
originally	O
allowed	O
only	O
in	O
FORMAT	O
and	O
DATA	O
statements	O
,	O
were	O
prefixed	O
by	O
a	O
character	O
count	O
and	O
the	O
letter	O
H	O
(	O
e.g.	O
,	O
)	O
,	O
allowing	O
blanks	O
to	O
be	O
retained	O
within	O
the	O
character	O
string	O
.	O
</s>
<s>
The	O
main	O
enhancement	O
was	O
to	O
support	O
procedural	B-Application
programming	I-Application
by	O
allowing	O
user-written	O
subroutines	O
and	O
functions	O
which	O
returned	O
values	O
with	O
parameters	O
passed	O
by	O
reference	O
.	O
</s>
<s>
Early	O
FORTRAN	O
compilers	B-Language
supported	O
no	O
recursion	O
in	O
subroutines	O
.	O
</s>
<s>
the	O
IBM	B-Device
1130	I-Device
)	O
or	O
a	O
specific	O
machine	O
register	O
(	O
IBM	B-Application
360	I-Application
et	O
seq	O
)	O
,	O
which	O
only	O
allows	O
recursion	O
if	O
a	O
stack	O
is	O
maintained	O
by	O
software	O
and	O
the	O
return	O
address	O
is	O
stored	O
on	O
the	O
stack	O
before	O
the	O
call	O
is	O
made	O
and	O
restored	O
after	O
the	O
call	O
returns	O
.	O
</s>
<s>
Although	O
not	O
specified	O
in	O
FORTRAN	O
77	O
,	O
many	O
F77	O
compilers	B-Language
supported	O
recursion	O
as	O
an	O
option	O
,	O
and	O
the	O
Burroughs	B-Device
mainframes	I-Device
,	O
designed	O
with	O
recursion	O
built-in	O
,	O
did	O
so	O
by	O
default	O
.	O
</s>
<s>
This	O
program	O
,	O
for	O
Heron	O
's	O
formula	O
,	O
reads	O
data	O
on	O
a	O
tape	O
reel	O
containing	O
three	O
5-digit	O
integers	O
A	O
,	O
B	O
,	O
and	O
C	B-Language
as	O
input	O
.	O
</s>
<s>
There	O
are	O
no	O
"	O
type	O
"	O
declarations	O
available	O
:	O
variables	O
whose	O
name	O
starts	O
with	O
I	O
,	O
J	O
,	O
K	O
,	O
L	O
,	O
M	B-Language
,	O
or	O
N	O
are	O
"	O
fixed-point	O
"	O
(	O
i.e.	O
</s>
<s>
integers	O
)	O
,	O
otherwise	O
floating-point	B-Algorithm
.	O
</s>
<s>
If	O
A	O
,	O
B	O
,	O
and	O
C	B-Language
cannot	O
represent	O
the	O
sides	O
of	O
a	O
triangle	O
in	O
plane	O
geometry	O
,	O
then	O
the	O
program	O
's	O
execution	O
will	O
end	O
with	O
an	O
error	O
code	O
of	O
"	O
STOP	O
1	O
"	O
.	O
</s>
<s>
Otherwise	O
,	O
an	O
output	O
line	O
will	O
be	O
printed	O
showing	O
the	O
input	O
values	O
for	O
A	O
,	O
B	O
,	O
and	O
C	B-Language
,	O
followed	O
by	O
the	O
computed	O
AREA	O
of	O
the	O
triangle	O
as	O
a	O
floating-point	B-Algorithm
number	I-Algorithm
occupying	O
ten	O
spaces	O
along	O
the	O
line	O
of	O
output	O
and	O
showing	O
2	O
digits	O
after	O
the	O
decimal	O
point	O
,	O
the	O
.2	O
in	O
F10.2	O
of	O
the	O
FORMAT	O
statement	O
with	O
label	O
601	O
.	O
</s>
<s>
IBM	O
also	O
developed	O
a	O
FORTRAN	O
III	O
in	O
1958	O
that	O
allowed	O
for	O
inline	B-Language
assembly	I-Language
code	O
among	O
other	O
features	O
;	O
however	O
,	O
this	O
version	O
was	O
never	O
released	O
as	O
a	O
product	O
.	O
</s>
<s>
FORTRAN	O
was	O
provided	O
for	O
the	O
IBM	B-Device
1401	I-Device
computer	O
by	O
an	O
innovative	O
63-phase	O
compiler	B-Language
that	O
ran	O
entirely	O
in	O
its	O
core	O
memory	O
of	O
only	O
8000	O
(	O
six-bit	O
)	O
characters	O
.	O
</s>
<s>
The	O
compiler	B-Language
could	O
be	O
run	O
from	O
tape	O
,	O
or	O
from	O
a	O
2200-card	O
deck	O
;	O
it	O
used	O
no	O
further	O
tape	O
or	O
disk	O
storage	O
.	O
</s>
<s>
It	O
kept	O
the	O
program	O
in	O
memory	O
and	O
loaded	O
overlays	B-General_Concept
that	O
gradually	O
transformed	O
it	O
,	O
in	O
place	O
,	O
into	O
executable	O
form	O
,	O
as	O
described	O
by	O
Haines	O
.	O
</s>
<s>
This	O
article	O
was	O
reprinted	O
,	O
edited	O
,	O
in	O
both	O
editions	O
of	O
Anatomy	O
of	O
a	O
Compiler	B-Language
and	O
in	O
the	O
IBM	O
manual	B-Protocol
"	O
Fortran	O
Specifications	O
and	O
Operating	O
Procedures	O
,	O
IBM	B-Device
1401	I-Device
"	O
.	O
</s>
<s>
The	O
executable	O
form	O
was	O
not	O
entirely	O
machine	B-Language
language	I-Language
;	O
rather	O
,	O
floating-point	B-Algorithm
arithmetic	I-Algorithm
,	O
sub-scripting	O
,	O
input/output	O
,	O
and	O
function	O
references	O
were	O
interpreted	O
,	O
preceding	O
UCSD	B-Language
Pascal	I-Language
P-code	O
by	O
two	O
decades	O
.	O
</s>
<s>
IBM	O
later	O
provided	O
a	O
FORTRAN	O
IV	O
compiler	B-Language
for	O
the	O
1400	O
series	O
of	O
computers	O
.	O
</s>
<s>
FORTRAN	O
IV	O
removed	O
the	O
machine-dependent	O
features	O
of	O
FORTRAN	O
II	O
(	O
such	O
as	O
)	O
,	O
while	O
adding	O
new	O
features	O
such	O
as	O
a	O
data	O
type	O
,	O
logical	O
Boolean	O
expressions	O
and	O
the	O
logical	O
IF	O
statement	O
as	O
an	O
alternative	O
to	O
the	O
arithmetic	B-Language
IF	I-Language
statement	O
.	O
</s>
<s>
FORTRAN	O
IV	O
was	O
eventually	O
released	O
in	O
1962	O
,	O
first	O
for	O
the	O
IBM	B-Device
7030	I-Device
(	O
"	O
Stretch	O
"	O
)	O
computer	O
,	O
followed	O
by	O
versions	O
for	O
the	O
IBM	B-Device
7090	I-Device
,	O
IBM	B-Device
7094	I-Device
,	O
and	O
later	O
for	O
the	O
IBM	B-Device
1401	I-Device
in	O
1966	O
.	O
</s>
<s>
By	O
1965	O
,	O
FORTRAN	O
IV	O
was	O
supposed	O
to	O
be	O
compliant	O
with	O
the	O
standard	O
being	O
developed	O
by	O
the	O
American	O
Standards	O
Association	O
X3.4.3	O
FORTRAN	O
Working	O
Group	O
.	O
</s>
<s>
Between	O
1966	O
and	O
1968	O
,	O
IBM	O
offered	O
several	O
FORTRAN	O
IV	O
compilers	B-Language
for	O
its	O
System/360	B-Application
,	O
each	O
named	O
by	O
letters	O
that	O
indicated	O
the	O
minimum	O
amount	O
of	O
memory	O
the	O
compiler	B-Language
needed	O
to	O
run	O
.	O
</s>
<s>
The	O
letters	O
(	O
F	B-Language
,	O
G	O
,	O
H	O
)	O
matched	O
the	O
codes	O
used	O
with	O
System/360	B-Application
model	O
numbers	O
to	O
indicate	O
memory	O
size	O
,	O
each	O
letter	O
increment	O
being	O
a	O
factor	O
of	O
two	O
larger	O
:	O
</s>
<s>
At	O
about	O
this	O
time	O
FORTRAN	O
IV	O
had	O
started	O
to	O
become	O
an	O
important	O
educational	O
tool	O
and	O
implementations	O
such	O
as	O
the	O
University	O
of	O
Waterloo	O
's	O
WATFOR	B-Language
and	O
WATFIV	B-Language
were	O
created	O
to	O
simplify	O
the	O
complex	O
compile	B-Language
and	O
link	O
processes	O
of	O
earlier	O
compilers	B-Language
.	O
</s>
<s>
After	O
the	O
release	O
of	O
the	O
FORTRAN	O
66	O
standard	O
,	O
compiler	B-Language
vendors	O
introduced	O
several	O
extensions	O
to	O
Standard	O
Fortran	O
,	O
prompting	O
ANSI	O
committee	O
X3J3	O
in	O
1969	O
to	O
begin	O
work	O
on	O
revising	O
the	O
1966	O
standard	O
,	O
under	O
sponsorship	O
of	O
CBEMA	O
,	O
the	O
Computer	O
Business	O
Equipment	O
Manufacturers	O
Association	O
(	O
formerly	O
BEMA	O
)	O
.	O
</s>
<s>
Generic	B-Language
names	O
for	O
intrinsic	B-Application
functions	I-Application
(	O
e.g.	O
</s>
<s>
A	O
set	O
of	O
intrinsics	O
(	O
)	O
for	O
lexical	O
comparison	O
of	O
strings	O
,	O
based	O
upon	O
the	O
ASCII	B-Protocol
collating	O
sequence	O
.	O
</s>
<s>
(	O
These	O
ASCII	B-Protocol
functions	O
were	O
demanded	O
by	O
the	O
U.S.	O
Department	O
of	O
Defense	O
,	O
in	O
their	O
conditional	O
approval	O
vote	O
.	O
)	O
</s>
<s>
(	O
Removal	O
was	O
the	O
only	O
allowable	O
alternative	O
to	O
X3J3	O
at	O
that	O
time	O
,	O
since	O
the	O
concept	O
of	O
"	O
deprecation	B-General_Concept
"	O
was	O
not	O
yet	O
available	O
for	O
ANSI	O
standards	O
.	O
)	O
</s>
<s>
This	O
specification	O
,	O
developed	O
by	O
the	O
U.S.	O
Department	O
of	O
Defense	O
,	O
standardized	O
a	O
number	O
of	O
features	O
implemented	O
by	O
most	O
FORTRAN	O
77	O
compilers	B-Language
but	O
not	O
included	O
in	O
the	O
ANSI	O
FORTRAN	O
77	O
standard	O
.	O
</s>
<s>
Free-form	B-Language
source	I-Language
input	I-Language
removed	O
the	O
need	O
to	O
skip	O
the	O
first	O
six	O
character	O
positions	O
before	O
entering	O
statements	O
.	O
</s>
<s>
Ability	O
to	O
operate	O
on	O
arrays	O
(	O
or	O
array	B-Application
sections	O
)	O
as	O
a	O
whole	O
,	O
thus	O
greatly	O
simplifying	O
math	O
and	O
engineering	O
computations	O
.	O
</s>
<s>
array-valued	O
constants	O
and	O
expressions	O
,	O
</s>
<s>
user-defined	O
array-valued	O
functions	O
and	O
array	B-Application
constructors	O
.	O
</s>
<s>
Modules	B-Architecture
,	O
to	O
group	O
related	O
procedures	O
and	O
data	O
together	O
,	O
and	O
make	O
them	O
available	O
to	O
other	O
program	O
units	O
,	O
including	O
the	O
capability	O
to	O
limit	O
the	O
accessibility	O
to	O
only	O
specific	O
parts	O
of	O
the	O
module	B-Architecture
.	O
</s>
<s>
New	O
and	O
enhanced	O
intrinsic	B-Application
procedures	O
.	O
</s>
<s>
Nevertheless	O
,	O
Fortran	O
95	O
also	O
added	O
a	O
number	O
of	O
extensions	O
,	O
notably	O
from	O
the	O
High	B-Language
Performance	I-Language
Fortran	I-Language
specification	O
:	O
</s>
<s>
A	O
number	O
of	O
intrinsic	B-Application
functions	I-Application
were	O
extended	O
(	O
for	O
example	O
a	O
argument	O
was	O
added	O
to	O
the	O
intrinsic	B-Application
)	O
.	O
</s>
<s>
This	O
specification	O
defined	O
enhanced	O
use	O
of	O
arrays	O
,	O
prior	O
to	O
the	O
availability	O
of	O
fully	O
Fortran	O
2003-compliant	O
Fortran	O
compilers	B-Language
.	O
</s>
<s>
(	O
arrays	O
are	O
preferable	O
to	O
-based	O
arrays	O
because	O
arrays	O
are	O
guaranteed	O
by	O
Fortran	O
95	O
to	O
be	O
deallocated	O
automatically	O
when	O
they	O
go	O
out	O
of	O
scope	O
,	O
eliminating	O
the	O
possibility	O
of	O
memory	O
leakage	B-Error_Name
.	O
</s>
<s>
In	O
addition	O
,	O
elements	O
of	O
allocatable	O
arrays	O
are	O
contiguous	O
,	O
and	O
aliasing	B-Application
is	O
not	O
an	O
issue	O
for	O
optimization	O
of	O
array	B-Application
references	O
,	O
allowing	O
compilers	B-Language
to	O
generate	O
faster	O
code	O
than	O
in	O
the	O
case	O
of	O
pointers	O
.	O
)	O
</s>
<s>
Another	O
important	O
supplement	O
to	O
Fortran	O
95	O
was	O
the	O
ISO	O
technical	O
report	O
TR-15580	O
:	O
Floating-point	B-Algorithm
exception	B-General_Concept
handling	I-General_Concept
,	O
informally	O
known	O
as	O
the	O
IEEE	O
TR	O
.	O
</s>
<s>
This	O
specification	O
defined	O
support	O
for	O
IEEE	O
floating-point	B-Algorithm
arithmetic	I-Algorithm
and	O
floating-point	B-Algorithm
exception	B-General_Concept
handling	I-General_Concept
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
mandatory	O
"	O
Base	O
language	O
"	O
(	O
defined	O
in	O
ISO/IEC	O
1539-1	O
:	O
1997	O
)	O
,	O
the	O
Fortran	O
95	O
language	O
also	O
includes	O
two	O
optional	O
modules	B-Architecture
:	O
</s>
<s>
According	O
to	O
the	O
standards	O
developers	O
,	O
"	O
the	O
optional	O
parts	O
describe	O
self-contained	O
features	O
which	O
have	O
been	O
requested	O
by	O
a	O
substantial	O
body	O
of	O
users	O
and/or	O
implementors	O
,	O
but	O
which	O
are	O
not	O
deemed	O
to	O
be	O
of	O
sufficient	O
generality	O
for	O
them	O
to	O
be	O
required	O
in	O
all	O
standard-conforming	O
Fortran	O
compilers.	O
"	O
</s>
<s>
The	O
language	O
defined	O
by	O
the	O
twenty-first	O
century	O
standards	O
,	O
in	O
particular	O
because	O
of	O
its	O
incorporation	O
of	O
Object-oriented	B-Language
programming	I-Language
support	O
and	O
subsequently	O
Coarray	B-Language
Fortran	I-Language
,	O
is	O
often	O
referred	O
to	O
as	O
'	O
Modern	O
Fortran	O
 '	O
,	O
and	O
the	O
term	O
is	O
increasingly	O
used	O
in	O
the	O
literature	O
.	O
</s>
<s>
An	O
important	O
supplement	O
to	O
Fortran	O
2003	O
was	O
the	O
ISO	O
technical	O
report	O
TR-19767	O
:	O
Enhanced	O
module	B-Architecture
facilities	O
in	O
Fortran	O
.	O
</s>
<s>
This	O
report	O
provided	O
sub-modules	O
,	O
which	O
make	O
Fortran	O
modules	B-Architecture
more	O
similar	O
to	O
Modula-2	B-Language
modules	B-Architecture
.	O
</s>
<s>
They	O
are	O
similar	O
to	O
Ada	B-Language
private	O
child	O
sub-units	O
.	O
</s>
<s>
This	O
allows	O
the	O
specification	O
and	O
implementation	O
of	O
a	O
module	B-Architecture
to	O
be	O
expressed	O
in	O
separate	O
program	O
units	O
,	O
which	O
improves	O
packaging	O
of	O
large	O
libraries	O
,	O
allows	O
preservation	O
of	O
trade	O
secrets	O
while	O
publishing	O
definitive	O
interfaces	O
,	O
and	O
prevents	O
compilation	B-Language
cascades	O
.	O
</s>
<s>
A	O
supplement	O
to	O
Fortran	O
2008	O
is	O
the	O
International	O
Organization	O
for	O
Standardization	O
(	O
ISO	O
)	O
Technical	O
Specification	O
(	O
TS	O
)	O
29113	O
on	O
Further	O
Interoperability	O
of	O
Fortran	O
with	O
C	B-Language
,	O
which	O
has	O
been	O
submitted	O
to	O
ISO	O
in	O
May	O
2012	O
for	O
approval	O
.	O
</s>
<s>
The	O
specification	O
adds	O
support	O
for	O
accessing	O
the	O
array	B-Application
descriptor	O
from	O
C	B-Language
and	O
allows	O
ignoring	O
the	O
type	O
and	O
rank	O
of	O
arguments	O
.	O
</s>
<s>
Additional	O
changes	O
and	O
new	O
features	O
include	O
support	O
for	O
ISO/IEC/IEEE	O
60559:2011	O
(	O
the	O
version	O
of	O
the	O
IEEE	O
floating-point	B-Algorithm
standard	O
before	O
the	O
latest	O
minor	O
revision	O
IEEE	O
)	O
,	O
hexadecimal	O
input/output	O
,	O
IMPLICIT	O
NONE	O
enhancements	O
and	O
other	O
changes	O
.	O
</s>
<s>
A	O
full	O
description	O
of	O
the	O
Fortran	B-Language
language	I-Language
features	I-Language
brought	O
by	O
Fortran	O
95	O
is	O
covered	O
in	O
the	O
related	O
article	O
,	O
Fortran	B-Language
95	I-Language
language	I-Language
features	I-Language
.	O
</s>
<s>
So	O
much	O
exists	O
in	O
FORTRAN	O
that	O
it	O
seems	O
unlikely	O
that	O
scientists	O
will	O
change	O
to	O
Pascal	B-Application
,	O
Modula-2	B-Language
,	O
or	O
whatever.	O
"	O
</s>
<s>
It	O
is	O
the	O
primary	O
language	O
for	O
some	O
of	O
the	O
most	O
intensive	O
super-computing	B-Architecture
tasks	O
,	O
such	O
as	O
in	O
astronomy	O
,	O
climate	B-Application
modeling	I-Application
,	O
computational	O
chemistry	O
,	O
computational	O
economics	O
,	O
computational	O
fluid	O
dynamics	O
,	O
computational	B-Algorithm
physics	I-Algorithm
,	O
data	O
analysis	O
,	O
hydrological	O
modeling	O
,	O
numerical	O
linear	O
algebra	O
and	O
numerical	O
libraries	O
(	O
LAPACK	B-Application
,	O
IMSL	B-Library
and	O
NAG	O
)	O
,	O
optimization	O
,	O
satellite	O
simulation	O
,	O
structural	O
engineering	O
,	O
and	O
weather	B-General_Concept
prediction	I-General_Concept
.	O
</s>
<s>
Many	O
of	O
the	O
floating-point	B-Algorithm
benchmarks	O
to	O
gauge	O
the	O
performance	O
of	O
new	O
computer	O
processors	O
,	O
such	O
as	O
the	O
floating-point	B-Algorithm
components	O
of	O
the	O
SPEC	O
benchmarks	O
(	O
e.g.	O
,	O
,	O
)	O
are	O
written	O
in	O
Fortran	O
.	O
</s>
<s>
Apart	O
from	O
this	O
,	O
more	O
modern	O
codes	O
in	O
computational	O
science	O
generally	O
use	O
large	O
program	O
libraries	O
,	O
such	O
as	O
METIS	B-Algorithm
for	O
graph	O
partitioning	O
,	O
PETSc	B-Language
or	O
Trilinos	B-Language
for	O
linear	O
algebra	O
capabilities	O
,	O
deal.II	B-Language
or	O
FEniCS	B-Language
for	O
mesh	O
and	O
finite	B-Application
element	I-Application
support	O
,	O
and	O
other	O
generic	B-Language
libraries	O
.	O
</s>
<s>
Since	O
the	O
early	O
2000s	O
,	O
many	O
of	O
the	O
widely	O
used	O
support	O
libraries	O
have	O
also	O
been	O
implemented	O
in	O
C	B-Language
and	O
more	O
recently	O
,	O
in	O
C++	B-Language
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
high-level	B-Language
languages	I-Language
such	O
as	O
the	O
Wolfram	B-Language
Language	I-Language
,	O
MATLAB	B-Language
,	O
Python	B-Language
,	O
and	O
R	B-Language
have	O
become	O
popular	O
in	O
particular	O
areas	O
of	O
computational	O
science	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
facilities	B-Application
for	I-Application
inter-operation	I-Application
with	I-Application
C	I-Application
were	O
added	O
to	O
Fortran	O
2003	O
and	O
enhanced	O
by	O
the	O
ISO/IEC	O
technical	O
specification	O
29113	O
,	O
which	O
was	O
incorporated	O
into	O
Fortran	O
2018	O
to	O
allow	O
more	O
flexible	O
interoperation	O
with	O
other	O
programming	O
languages	O
.	O
</s>
<s>
Software	O
for	O
NASA	O
probes	O
Voyager	O
1	O
and	O
Voyager	O
2	O
was	O
originally	O
written	O
in	O
FORTRAN	O
5	O
,	O
and	O
later	O
ported	O
to	O
FORTRAN	O
77	O
.	O
,	O
some	O
of	O
the	O
software	O
is	O
still	O
written	O
in	O
Fortran	O
and	O
some	O
has	O
been	O
ported	O
to	O
C	B-Language
.	O
</s>
<s>
Portability	O
was	O
a	O
problem	O
in	O
the	O
early	O
days	O
because	O
there	O
was	O
no	O
agreed	O
upon	O
standard	O
—	O
not	O
even	O
IBM	O
's	O
reference	O
manual	B-Protocol
—	O
and	O
computer	O
companies	O
vied	O
to	O
differentiate	O
their	O
offerings	O
from	O
others	O
by	O
providing	O
incompatible	O
features	O
.	O
</s>
<s>
Rather	O
than	O
offer	O
two	O
processors	O
,	O
essentially	O
every	O
compiler	B-Language
eventually	O
had	O
at	O
least	O
an	O
option	O
to	O
diagnose	O
extensions	O
.	O
</s>
<s>
For	O
numerical	B-General_Concept
calculations	I-General_Concept
,	O
it	O
is	O
important	O
to	O
take	O
account	O
of	O
the	O
characteristics	O
of	O
the	O
arithmetic	O
.	O
</s>
<s>
The	O
ideas	O
therein	O
became	O
widely	O
used	O
,	O
and	O
were	O
eventually	O
incorporated	O
into	O
the	O
1990	O
standard	O
by	O
way	O
of	O
intrinsic	B-Application
inquiry	O
functions	O
.	O
</s>
<s>
The	O
widespread	O
(	O
now	O
almost	O
universal	O
)	O
adoption	O
of	O
the	O
IEEE	O
754	O
standard	O
for	O
binary	B-Algorithm
floating-point	I-Algorithm
arithmetic	I-Algorithm
has	O
essentially	O
removed	O
this	O
problem	O
.	O
</s>
<s>
Access	O
to	O
the	O
computing	O
environment	O
(	O
e.g.	O
,	O
the	O
program	O
's	O
command	B-Application
line	I-Application
,	O
environment	O
variables	O
,	O
textual	O
explanation	O
of	O
error	O
conditions	O
)	O
remained	O
a	O
problem	O
until	O
it	O
was	O
addressed	O
by	O
the	O
2003	O
standard	O
.	O
</s>
<s>
Large	O
collections	O
of	O
library	O
software	O
that	O
could	O
be	O
described	O
as	O
being	O
loosely	O
related	O
to	O
engineering	O
and	O
scientific	O
calculations	O
,	O
such	O
as	O
graphics	O
libraries	O
,	O
have	O
been	O
written	O
in	O
C	B-Language
,	O
and	O
therefore	O
access	O
to	O
them	O
presented	O
a	O
portability	O
problem	O
.	O
</s>
<s>
This	O
has	O
been	O
addressed	O
by	O
incorporation	O
of	O
C	B-Language
interoperability	O
into	O
the	O
2003	O
standard	O
.	O
</s>
<s>
It	O
is	O
now	O
possible	O
(	O
and	O
relatively	O
easy	O
)	O
to	O
write	O
an	O
entirely	O
portable	O
program	O
in	O
Fortran	O
,	O
even	O
without	O
recourse	O
to	O
a	O
preprocessor	B-General_Concept
.	O
</s>
<s>
Until	O
the	O
Fortran	O
66	O
standard	O
was	O
developed	O
,	O
each	O
compiler	B-Language
supported	O
its	O
own	O
variant	O
of	O
Fortran	O
.	O
</s>
<s>
The	O
first	O
Fortran	O
compiler	B-Language
set	O
a	O
high	O
standard	O
of	O
efficiency	O
for	O
compiled	B-Language
code	O
.	O
</s>
<s>
This	O
goal	O
made	O
it	O
difficult	O
to	O
create	O
a	O
compiler	B-Language
so	O
it	O
was	O
usually	O
done	O
by	O
the	O
computer	O
manufacturers	O
to	O
support	O
hardware	O
sales	O
.	O
</s>
<s>
This	O
left	O
an	O
important	O
niche	O
:	O
compilers	B-Language
that	O
were	O
fast	O
and	O
provided	O
good	O
diagnostics	O
for	O
the	O
programmer	O
(	O
often	O
a	O
student	O
)	O
.	O
</s>
<s>
Examples	O
include	O
Watfor	B-Language
,	O
Watfiv	B-Language
,	O
PUFFT	O
,	O
and	O
on	O
a	O
smaller	O
scale	O
,	O
FORGO	O
,	O
Wits	O
Fortran	O
,	O
and	O
Kingston	O
Fortran	O
2	O
.	O
</s>
<s>
Fortran	O
5	O
was	O
marketed	O
by	O
Data	O
General	O
Corp	O
in	O
the	O
late	O
1970s	O
and	O
early	O
1980s	O
,	O
for	O
the	O
Nova	B-Device
,	O
Eclipse	B-Device
,	O
and	O
MV	B-Device
line	O
of	O
computers	O
.	O
</s>
<s>
It	O
had	O
an	O
optimizing	B-Application
compiler	I-Application
that	O
was	O
quite	O
good	O
for	O
minicomputers	O
of	O
its	O
time	O
.	O
</s>
<s>
FORTRAN	O
V	O
was	O
distributed	O
by	O
Control	O
Data	O
Corporation	O
in	O
1968	O
for	O
the	O
CDC	B-Device
6600	I-Device
series	O
.	O
</s>
<s>
Univac	O
also	O
offered	O
a	O
compiler	B-Language
for	O
the	O
1100	O
series	O
known	O
as	O
FORTRAN	O
V	O
.	O
A	O
spinoff	O
of	O
Univac	O
Fortran	O
V	O
was	O
Athena	O
FORTRAN	O
.	O
</s>
<s>
Specific	O
variants	O
produced	O
by	O
the	O
vendors	O
of	O
high-performance	O
scientific	O
computers	O
(	O
e.g.	O
,	O
Burroughs	O
,	O
Control	O
Data	O
Corporation	O
(	O
CDC	O
)	O
,	O
Cray	O
,	O
Honeywell	O
,	O
IBM	O
,	O
Texas	O
Instruments	O
,	O
and	O
UNIVAC	O
)	O
added	O
extensions	O
to	O
Fortran	O
to	O
take	O
advantage	O
of	O
special	O
hardware	O
features	O
such	O
as	O
instruction	B-General_Concept
cache	I-General_Concept
,	O
CPU	B-General_Concept
pipelines	I-General_Concept
,	O
and	O
vector	O
arrays	O
.	O
</s>
<s>
For	O
example	O
,	O
one	O
of	O
IBM	O
's	O
FORTRAN	O
compilers	B-Language
(	O
H	O
Extended	O
IUP	O
)	O
had	O
a	O
level	O
of	O
optimization	O
which	O
reordered	O
the	O
machine	B-Language
code	I-Language
instructions	O
to	O
keep	O
multiple	O
internal	O
arithmetic	O
units	O
busy	O
simultaneously	O
.	O
</s>
<s>
Another	O
example	O
is	O
CFD	O
,	O
a	O
special	O
variant	O
of	O
FORTRAN	O
designed	O
specifically	O
for	O
the	O
ILLIAC	B-Device
IV	I-Device
supercomputer	B-Architecture
,	O
running	O
at	O
NASA	O
's	O
Ames	O
Research	O
Center	O
.	O
</s>
<s>
Object-Oriented	B-Language
Fortran	I-Language
was	O
an	O
object-oriented	B-Language
extension	O
of	O
Fortran	O
,	O
in	O
which	O
data	O
items	O
can	O
be	O
grouped	O
into	O
objects	O
,	O
which	O
can	O
be	O
instantiated	O
and	O
executed	O
in	O
parallel	O
.	O
</s>
<s>
It	O
was	O
available	O
for	O
Sun	O
,	O
Iris	O
,	O
iPSC	B-Device
,	O
and	O
nCUBE	O
,	O
but	O
is	O
no	O
longer	O
supported	O
.	O
</s>
<s>
The	O
major	O
remaining	O
extension	O
is	O
OpenMP	B-Application
,	O
which	O
is	O
a	O
cross-platform	B-Operating_System
extension	O
for	O
shared	O
memory	O
programming	O
.	O
</s>
<s>
One	O
new	O
extension	O
,	O
Coarray	B-Language
Fortran	I-Language
,	O
is	O
intended	O
to	O
support	O
parallel	B-Operating_System
programming	I-Operating_System
.	O
</s>
<s>
FOR	B-Language
TRANSIT	I-Language
was	O
the	O
name	O
of	O
a	O
reduced	O
version	O
of	O
the	O
IBM	B-Device
704	I-Device
FORTRAN	O
language	O
,	O
</s>
<s>
The	O
following	O
comment	O
appears	O
in	O
the	O
IBM	O
Reference	O
Manual	B-Protocol
(	O
FOR	B-Language
TRANSIT	I-Language
Automatic	O
Coding	O
System	O
C28-4038	O
,	O
Copyright	O
1957	O
,	O
1959	O
by	O
IBM	O
)	O
:	O
</s>
<s>
The	O
FORTRAN	O
system	O
was	O
designed	O
for	O
a	O
more	O
complex	O
machine	O
than	O
the	O
650	B-Device
,	O
and	O
consequently	O
some	O
of	O
the	O
32	O
statements	O
found	O
in	O
the	O
FORTRAN	O
Programmer	O
's	O
Reference	O
Manual	B-Protocol
are	O
not	O
acceptable	O
to	O
the	O
FOR	B-Language
TRANSIT	I-Language
system	O
.	O
</s>
<s>
However	O
,	O
none	O
of	O
these	O
restrictions	O
make	O
a	O
source	O
program	O
written	O
for	O
FOR	B-Language
TRANSIT	I-Language
incompatible	O
with	O
the	O
FORTRAN	O
system	O
for	O
the	O
704	O
.	O
</s>
<s>
FOR	B-Language
TRANSIT	I-Language
statements	O
were	O
limited	O
to	O
columns	O
7	O
through	O
56	O
,	O
only	O
.	O
</s>
<s>
Punched	B-Architecture
cards	I-Architecture
were	O
used	O
for	O
input	O
and	O
output	O
on	O
the	O
IBM	B-Device
650	I-Device
.	O
</s>
<s>
Three	O
passes	O
were	O
required	O
to	O
translate	O
source	O
code	O
to	O
the	O
"	O
IT	O
"	O
language	O
,	O
then	O
to	O
compile	B-Language
the	O
IT	O
statements	O
into	O
SOAP	O
assembly	B-Language
language	I-Language
,	O
and	O
finally	O
to	O
produce	O
the	O
object	O
program	O
,	O
which	O
could	O
then	O
be	O
loaded	O
into	O
the	O
machine	O
to	O
run	O
the	O
program	O
(	O
using	O
punched	B-Architecture
cards	I-Architecture
for	O
data	O
input	O
,	O
and	O
outputting	O
results	O
onto	O
punched	B-Architecture
cards	I-Architecture
)	O
.	O
</s>
<s>
Two	O
versions	O
existed	O
for	O
the	O
650s	O
with	O
a	O
2000	O
word	O
memory	O
drum	O
:	O
FOR	B-Language
TRANSIT	I-Language
I	O
(	O
S	O
)	O
and	O
FOR	B-Language
TRANSIT	I-Language
II	O
,	O
the	O
latter	O
for	O
machines	O
equipped	O
with	O
indexing	O
registers	O
and	O
automatic	O
floating-point	B-Algorithm
decimal	O
(	O
bi-quinary	B-Algorithm
)	O
arithmetic	O
.	O
</s>
<s>
Appendix	O
A	O
of	O
the	O
manual	B-Protocol
included	O
wiring	O
diagrams	O
for	O
the	O
IBM	B-Device
533	I-Device
card	O
reader/punch	O
control	O
panel	O
.	O
</s>
<s>
Prior	O
to	O
FORTRAN	O
77	O
,	O
a	O
number	O
of	O
preprocessors	B-General_Concept
were	O
commonly	O
used	O
to	O
provide	O
a	O
friendlier	O
language	O
,	O
with	O
the	O
advantage	O
that	O
the	O
preprocessed	O
code	O
could	O
be	O
compiled	B-Language
on	O
any	O
machine	O
with	O
a	O
standard	O
FORTRAN	O
compiler	B-Language
.	O
</s>
<s>
These	O
preprocessors	B-General_Concept
would	O
typically	O
support	O
structured	B-Language
programming	I-Language
,	O
variable	O
names	O
longer	O
than	O
six	O
characters	O
,	O
additional	O
data	O
types	O
,	O
conditional	B-Application
compilation	I-Application
,	O
and	O
even	O
macro	O
capabilities	O
.	O
</s>
<s>
Popular	O
preprocessors	B-General_Concept
included	O
EFL	B-Language
,	O
FLECS	O
,	O
iftran	B-Language
,	O
MORTRAN	B-Language
,	O
SFtran	O
,	O
S-Fortran	O
,	O
Ratfor	B-Language
,	O
and	O
Ratfiv	O
.	O
</s>
<s>
Ratfor	B-Language
and	O
Ratfiv	O
,	O
for	O
example	O
,	O
implemented	O
a	O
C-like	O
language	O
,	O
outputting	O
preprocessed	O
code	O
in	O
standard	O
FORTRAN	O
66	O
.	O
</s>
<s>
Despite	O
advances	O
in	O
the	O
Fortran	O
language	O
,	O
preprocessors	B-General_Concept
continue	O
to	O
be	O
used	O
for	O
conditional	B-Application
compilation	I-Application
and	O
macro	O
substitution	O
.	O
</s>
<s>
Developed	O
,	O
supported	O
,	O
and	O
distributed	O
by	O
the	O
University	O
of	O
Waterloo	O
,	O
WATFOR	B-Language
was	O
based	O
largely	O
on	O
FORTRAN	O
IV	O
.	O
</s>
<s>
A	O
student	O
using	O
WATFOR	B-Language
could	O
submit	O
their	O
batch	O
FORTRAN	O
job	O
and	O
,	O
if	O
there	O
were	O
no	O
syntax	O
errors	O
,	O
the	O
program	O
would	O
move	O
straight	O
to	O
execution	O
.	O
</s>
<s>
This	O
simplification	O
allowed	O
students	O
to	O
concentrate	O
on	O
their	O
program	O
's	O
syntax	O
and	O
semantics	O
,	O
or	O
execution	O
logic	O
flow	O
,	O
rather	O
than	O
dealing	O
with	O
submission	O
Job	B-Application
Control	I-Application
Language	I-Application
(	O
JCL	O
)	O
,	O
the	O
compile/link-edit/execution	O
successive	O
process(es )	O
,	O
or	O
other	O
complexities	O
of	O
the	O
mainframe/minicomputer	O
environment	O
.	O
</s>
<s>
A	O
down	O
side	O
to	O
this	O
simplified	O
environment	O
was	O
that	O
WATFOR	B-Language
was	O
not	O
a	O
good	O
choice	O
for	O
programmers	O
needing	O
the	O
expanded	O
abilities	O
of	O
their	O
host	O
processor(s )	O
,	O
e.g.	O
,	O
WATFOR	B-Language
typically	O
had	O
very	O
limited	O
access	O
to	O
I/O	O
devices	O
.	O
</s>
<s>
WATFOR	B-Language
was	O
succeeded	O
by	O
WATFIV	B-Language
and	O
its	O
later	O
versions	O
.	O
</s>
<s>
LRLTRAN	O
was	O
developed	O
at	O
the	O
Lawrence	O
Radiation	O
Laboratory	O
to	O
provide	O
support	O
for	O
vector	O
arithmetic	O
and	O
dynamic	B-General_Concept
storage	I-General_Concept
,	O
among	O
other	O
extensions	O
to	O
support	O
systems	O
programming	O
.	O
</s>
<s>
The	O
Fortran-95	O
Standard	O
includes	O
an	O
optional	O
Part	O
3	O
which	O
defines	O
an	O
optional	O
conditional	B-Application
compilation	I-Application
capability	O
.	O
</s>
<s>
Many	O
Fortran	O
compilers	B-Language
have	O
integrated	O
subsets	O
of	O
the	O
C	B-Language
preprocessor	I-Language
into	O
their	O
systems	O
.	O
</s>
<s>
SIMSCRIPT	B-Language
is	O
an	O
application	O
specific	O
Fortran	O
preprocessor	B-General_Concept
for	O
modeling	O
and	O
simulating	O
large	O
discrete	O
systems	O
.	O
</s>
<s>
The	O
F	B-Language
programming	I-Language
language	I-Language
was	O
designed	O
to	O
be	O
a	O
clean	O
subset	O
of	O
Fortran	O
95	O
that	O
attempted	O
to	O
remove	O
the	O
redundant	O
,	O
unstructured	O
,	O
and	O
deprecated	B-General_Concept
features	O
of	O
Fortran	O
,	O
such	O
as	O
the	O
statement	O
.	O
</s>
<s>
F	B-Language
retains	O
the	O
array	B-Application
features	O
added	O
in	O
Fortran	O
90	O
,	O
and	O
removes	O
control	O
statements	O
that	O
were	O
made	O
obsolete	O
by	O
structured	B-Language
programming	I-Language
constructs	O
added	O
to	O
both	O
FORTRAN	O
77	O
and	O
Fortran	O
90	O
.	O
</s>
<s>
F	B-Language
is	O
described	O
by	O
its	O
creators	O
as	O
"	O
a	O
compiled	B-Language
,	O
structured	B-Language
,	O
array	B-Application
programming	I-Application
language	I-Application
especially	O
well	O
suited	O
to	O
education	O
and	O
scientific	O
computing	O
"	O
.	O
</s>
<s>
Lahey	O
and	O
Fujitsu	O
teamed	O
up	O
to	O
create	O
Fortran	O
for	O
the	O
Microsoft	B-Application
.NET	I-Application
Framework	I-Application
.	O
</s>
<s>
Silverfrost	B-Application
FTN95	I-Application
is	O
also	O
capable	O
of	O
creating	O
.NET	B-Application
code	O
.	O
</s>
<s>
The	O
following	O
program	O
illustrates	O
dynamic	B-General_Concept
memory	I-General_Concept
allocation	I-General_Concept
and	O
array-based	O
operations	O
,	O
two	O
features	O
introduced	O
with	O
Fortran	O
90	O
.	O
</s>
<s>
Particularly	O
noteworthy	O
is	O
the	O
absence	O
of	O
loops	O
and	O
/	O
statements	O
in	O
manipulating	O
the	O
array	B-Application
;	O
mathematical	O
operations	O
are	O
applied	O
to	O
the	O
array	B-Application
as	O
a	O
whole	O
.	O
</s>
<s>
This	O
was	O
considered	O
beneficial	O
in	O
that	O
it	O
would	O
promote	O
structured	B-Language
programming	I-Language
,	O
by	O
making	O
it	O
impossible	O
to	O
use	O
the	O
notorious	O
statement	O
as	O
before	O
.	O
</s>
