<s>
IRAF	B-Application
(	O
Image	B-Application
Reduction	I-Application
and	I-Application
Analysis	I-Application
Facility	I-Application
)	O
is	O
a	O
collection	O
of	O
software	O
written	O
at	O
the	O
National	O
Optical	O
Astronomy	O
Observatory	O
(	O
NOAO	O
)	O
geared	O
towards	O
the	O
reduction	O
of	O
astronomical	O
images	O
and	O
spectra	O
in	O
pixel	O
array	O
form	O
.	O
</s>
<s>
This	O
is	O
primarily	O
data	O
taken	O
from	O
imaging	O
array	O
detectors	O
such	O
as	O
CCDs	B-Algorithm
.	O
</s>
<s>
It	O
is	O
available	O
for	O
all	O
major	O
operating	B-General_Concept
systems	I-General_Concept
for	O
mainframes	B-Architecture
and	O
desktop	O
computers	O
.	O
</s>
<s>
IRAF	B-Application
was	O
designed	O
cross-platform	O
,	O
supporting	O
VMS	B-Operating_System
and	O
UNIX-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
.	O
</s>
<s>
Use	O
on	O
Microsoft	B-Application
Windows	I-Application
was	O
made	O
possible	O
by	O
Cygwin	B-Language
in	O
earlier	O
versions	O
,	O
and	O
can	O
be	O
today	O
done	O
with	O
the	O
Windows	O
Subsystem	O
for	O
Linux	B-Application
.	O
</s>
<s>
Today	O
,	O
it	O
is	O
primarily	O
used	O
on	O
macOS	B-Application
and	O
Linux	B-Application
.	O
</s>
<s>
IRAF	B-Application
commands	O
(	O
known	O
as	O
tasks	O
)	O
are	O
organized	O
into	O
package	O
structures	O
.	O
</s>
<s>
Additional	O
packages	O
may	O
be	O
added	O
to	O
IRAF	B-Application
.	O
</s>
<s>
Functionality	O
available	O
in	O
IRAF	B-Application
includes	O
the	O
calibration	O
of	O
the	O
fluxes	O
and	O
positions	O
of	O
astronomical	O
objects	O
within	O
an	O
image	O
,	O
compensation	O
for	O
sensitivity	O
variations	O
between	O
detector	O
pixels	O
,	O
combination	O
of	O
multiple	O
images	O
or	O
measurement	O
of	O
the	O
redshifts	B-Application
of	O
absorption	O
or	O
emission	O
lines	O
in	O
a	O
spectrum	O
.	O
</s>
<s>
While	O
IRAF	B-Application
is	O
still	O
very	O
popular	O
among	O
astronomers	O
,	O
institutional	O
development	O
and	O
maintenance	O
was	O
stopped	O
.	O
</s>
<s>
IRAF	B-Application
is	O
now	O
maintained	O
as	O
community	O
software	O
.	O
</s>
<s>
The	O
IRAF	B-Application
project	O
started	O
in	O
fall	O
1981	O
at	O
Kitt	O
Peak	O
National	O
Observatory	O
.	O
</s>
<s>
The	O
IRAF	B-Application
Group	O
was	O
founded	O
.	O
</s>
<s>
Designer	O
of	O
the	O
IRAF	B-Application
system	O
and	O
chief	O
programmer	O
was	O
Doug	O
Tody	O
.	O
</s>
<s>
In	O
1983	O
,	O
Space	O
Telescope	O
Science	O
Institute	O
selected	O
IRAF	B-Application
as	O
the	O
environment	O
for	O
their	O
SDAS	O
data	O
analysis	O
system	O
and	O
ported	O
the	O
system	O
to	O
VMS	B-Operating_System
.	O
</s>
<s>
The	O
first	O
internal	O
IRAF	B-Application
release	O
was	O
in	O
1984	O
.	O
</s>
<s>
In	O
the	O
middle	O
of	O
the	O
1990s	O
,	O
the	O
"	O
Open	O
IRAF	B-Application
"	O
project	O
was	O
started	O
to	O
address	O
the	O
problems	O
that	O
were	O
seen	O
at	O
that	O
time	O
.	O
</s>
<s>
This	O
included	O
language	O
bindings	O
,	O
a	O
way	O
to	O
use	O
IRAF	B-Application
components	O
without	O
the	O
full	O
IRAF	B-Application
environment	O
,	O
new	O
data	O
types	O
and	O
dynamically	O
loadable	O
user	O
code	O
.	O
</s>
<s>
At	O
the	O
end	O
of	O
the	O
1990s	O
,	O
the	O
IRAF	B-Application
development	O
slowed	O
down	O
considerably	O
,	O
as	O
the	O
system	O
was	O
considered	O
mature	O
.	O
</s>
<s>
However	O
,	O
voluntary	O
work	O
of	O
the	O
IRAF	B-Application
developers	O
continued	O
and	O
they	O
distributed	O
some	O
unofficial	O
intermediary	O
versions	O
.	O
</s>
<s>
From	O
2006	O
to	O
2009	O
,	O
a	O
first	O
effort	O
was	O
made	O
to	O
port	O
IRAF	B-Application
to	O
64	O
bit	O
at	O
the	O
Institute	O
of	O
Space	O
and	O
Astronautical	O
Science	O
Japan	O
.	O
</s>
<s>
While	O
this	O
effort	O
did	O
not	O
evolve	O
into	O
a	O
new	O
official	O
IRAF	B-Application
version	O
,	O
it	O
contributed	O
significant	O
portions	O
to	O
the	O
64-bit	O
port	O
by	O
NOAO	O
.	O
</s>
<s>
In	O
2017	O
,	O
the	O
source	O
code	O
was	O
transferred	O
to	O
GitHub	B-Application
.	O
</s>
<s>
In	O
an	O
effort	O
to	O
package	O
the	O
IRAF	B-Application
software	O
for	O
Debian	O
,	O
it	O
was	O
cleaned	O
up	O
from	O
the	O
remaining	O
non-free	O
source	O
code	O
and	O
is	O
maintained	O
solely	O
by	O
the	O
community	O
since	O
then	O
.	O
</s>
<s>
The	O
licensing	O
status	O
of	O
IRAF	B-Application
generally	O
follows	O
the	B-License
MIT	I-License
license	I-License
scheme	O
.	O
</s>
<s>
In	O
particular	O
,	O
the	O
NCAR	O
graphics	O
code	O
restricted	O
re-distribution	O
of	O
IRAF	B-Application
before	O
it	O
was	O
removed	O
in	O
version	O
2.16	O
.	O
</s>
<s>
This	O
allowed	O
the	O
distribution	O
of	O
IRAF	B-Application
packages	O
in	O
mainstream	O
Linux	B-Application
distributions	O
like	O
Debian	O
or	O
Ubuntu	O
.	O
</s>
<s>
Four	O
basic	O
components	O
make	B-Application
up	O
the	O
run-time	O
IRAF	B-Application
system	O
:	O
</s>
<s>
The	O
Applications	O
Packages	O
are	O
a	O
structured	O
collection	O
of	O
portable	O
tasks	O
for	O
scientific	O
data	B-General_Concept
reduction	I-General_Concept
and	O
analysis	O
,	O
but	O
also	O
for	O
system	O
utilities	O
.	O
</s>
<s>
The	O
Virtual	O
Operation	B-General_Concept
System	I-General_Concept
(	O
VOS	O
)	O
provides	O
a	O
portable	O
interface	O
for	O
the	O
application	O
tasks	O
.	O
</s>
<s>
It	O
is	O
modeled	O
after	O
the	O
Unix	O
system	O
functions	O
,	O
but	O
with	O
an	O
API	O
for	O
the	O
IRAF	B-Application
specific	O
Subset	O
Preprocessor	B-General_Concept
language	O
(	O
SPP	O
)	O
.	O
</s>
<s>
They	O
can	O
be	O
divided	O
into	O
two	O
classes	O
:	O
general	O
system	O
and	O
basic	O
dataprocessing	O
utilities	O
,	O
and	O
packages	O
specific	O
to	O
astronomical	O
data	B-General_Concept
reduction	I-General_Concept
and	O
analysis	O
.	O
</s>
<s>
The	O
system	O
packages	O
are	O
located	O
in	O
the	O
base	O
package	O
of	O
IRAF	B-Application
and	O
provide	O
tools	O
for	O
the	O
CL	O
,	O
useful	O
operating	B-General_Concept
system	I-General_Concept
utilities	O
,	O
and	O
basic	O
scientific	O
utilities	O
,	O
f.e.	O
</s>
<s>
dataio	O
Data	O
format	O
conversion	O
(	O
FITS	O
,	O
IRAF	B-Application
image	O
format	O
etc	O
.	O
)	O
</s>
<s>
Most	O
of	O
these	O
tasks	O
are	O
general	O
,	O
but	O
the	O
imred	O
package	O
also	O
contains	O
data	B-General_Concept
reduction	I-General_Concept
tasks	O
for	O
specific	O
instruments	O
.	O
</s>
<s>
onedspec	O
One	O
dimensional	O
spectral	O
data	B-General_Concept
reduction	I-General_Concept
and	O
analysis	O
package	O
.	O
</s>
<s>
One	O
strength	O
of	O
IRAF	B-Application
was	O
the	O
existence	O
of	O
various	O
external	O
packages	O
,	O
which	O
resolved	O
specific	O
problems	O
or	O
implemented	O
specialized	O
data	B-General_Concept
reduction	I-General_Concept
pipelines	O
.	O
</s>
<s>
stsdas	B-Application
Software	O
system	O
from	O
Space	O
Telescope	O
Science	O
Institute	O
for	O
calibrating	O
and	O
analyzing	O
data	O
from	O
the	O
Hubble	O
Space	O
Telescope	O
(	O
the	O
original	O
tables	O
package	O
from	O
STSci	O
is	O
included	O
as	O
utilities.nttables	O
in	O
the	O
system	O
packages	O
)	O
.	O
</s>
<s>
IRAF	B-Application
allows	O
users	O
to	O
write	O
their	O
own	O
tasks	O
in	O
two	O
main	O
ways	O
.	O
</s>
<s>
There	O
are	O
three	O
types	O
of	O
tasks	O
the	O
CL	O
can	O
execute	O
:	O
native	O
tasks	O
,	O
which	O
are	O
part	O
of	O
compiled	O
IRAF	B-Application
executables	O
,	O
scripts	O
(	O
CL	O
tasks	O
which	O
are	O
tasks	O
written	O
in	O
CL	O
)	O
,	O
and	O
foreign	O
tasks	O
,	O
external	O
programs	O
or	O
scripts	O
that	O
are	O
executed	O
by	O
the	O
CL	O
.	O
</s>
<s>
CL	O
scripts	O
have	O
usually	O
the	O
suffix	O
.cl	O
,	O
which	O
may	O
cause	O
conflicts	O
with	O
Common	B-Language
Lisp	I-Language
code	O
files	O
.	O
</s>
<s>
The	O
subset	O
preprocessor	B-General_Concept
language	O
(	O
SPP	O
)	O
implements	O
a	O
subset	O
of	O
the	O
IRAF	B-Application
preprocessor	B-General_Concept
language	O
that	O
was	O
planned	O
in	O
the	O
early	O
days	O
of	O
IRAF	B-Application
.	O
</s>
<s>
The	O
SPP	O
language	O
is	O
based	O
on	O
the	O
Ratfor	B-Language
language	O
.	O
</s>
<s>
The	O
lexical	O
form	O
,	O
operators	O
,	O
and	O
control	O
flow	O
constructs	O
are	O
identical	O
to	O
those	O
provided	O
by	O
Ratfor	B-Language
.	O
</s>
<s>
The	O
xc	O
program	O
,	O
provided	O
with	O
IRAF	B-Application
,	O
translates	O
SPP	O
programs	O
into	O
Fortran	O
66	O
,	O
and	O
from	O
there	O
with	O
f2c	B-Language
into	O
C	O
code	O
.	O
</s>
<s>
The	O
preprocessor	B-General_Concept
is	O
complemented	O
with	O
mkpkg	O
,	O
a	O
make	B-Application
like	O
build	O
automation	O
tool	O
,	O
generic	O
,	O
a	O
tool	O
to	O
translate	O
generic	B-Language
types	I-Language
into	O
type	O
dependent	O
source	O
code	O
,	O
and	O
xyacc	O
,	O
a	O
modified	O
yacc	B-Application
to	O
produce	O
SPP	O
output	O
.	O
</s>
<s>
A	O
full	O
IRAF	B-Application
working	O
environment	O
usually	O
requires	O
two	O
other	O
applications	O
:	O
an	O
extended	O
xterm	O
window	O
with	O
a	O
graphics	O
windows	O
(	O
called	O
xgterm	O
and	O
distributed	O
in	O
a	O
separate	O
x11iraf	O
package	O
)	O
and	O
an	O
image	O
display	O
program	O
referred	O
to	O
as	O
an	O
"	O
image	O
server	O
"	O
.	O
</s>
<s>
As	O
an	O
alternative	O
of	O
xgterm	O
and	O
the	O
Command	O
Language	O
,	O
the	O
Python	B-Language
package	O
PyRAF	O
can	O
be	O
used	O
.	O
</s>
<s>
PyRAF	O
is	O
able	O
to	O
translate	O
CL	O
scripts	O
into	O
Python	B-Language
scripts	I-Language
.	O
</s>
<s>
It	O
also	O
provides	O
a	O
graphics	O
window	O
(	O
based	O
on	O
Tk	B-Application
or	O
on	O
Matplotlib	B-Language
)	O
.	O
</s>
<s>
As	O
command	O
shell	O
,	O
either	O
the	O
Python	B-Language
or	O
IPython	B-Application
command	O
shell	O
can	O
be	O
used	O
,	O
or	O
a	O
special	O
mode	O
resembling	O
much	O
of	O
the	O
look	O
and	O
feel	O
of	O
the	O
CL	O
command	O
shell	O
.	O
</s>
