<s>
Apple	B-Operating_System
DOS	I-Operating_System
is	O
the	O
family	O
of	O
disk	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
for	O
the	O
Apple	B-Device
II	I-Device
series	I-Device
of	O
microcomputers	B-Device
from	O
late	O
1978	O
through	O
early	O
1983	O
.	O
</s>
<s>
It	O
was	O
superseded	O
by	O
ProDOS	B-Operating_System
in	O
1983	O
.	O
</s>
<s>
Apple	B-Operating_System
DOS	I-Operating_System
has	O
three	O
major	O
releases	O
:	O
DOS	O
3.1	O
,	O
DOS	O
3.2	O
,	O
and	O
DOS	O
3.3	O
;	O
each	O
one	O
of	O
these	O
three	O
releases	O
was	O
followed	O
by	O
a	O
second	O
,	O
minor	O
"	O
bug-fix	O
"	O
release	O
,	O
but	O
only	O
in	O
the	O
case	O
of	O
Apple	B-Operating_System
DOS	I-Operating_System
3.2	O
did	O
that	O
minor	O
release	O
receive	O
its	O
own	O
version	O
number	O
,	O
Apple	B-Operating_System
DOS	I-Operating_System
3.2.1	O
.	O
</s>
<s>
The	O
best-known	O
and	O
most-used	O
version	O
is	O
Apple	B-Operating_System
DOS	I-Operating_System
3.3	O
in	O
the	O
1980	O
and	O
1983	O
releases	O
.	O
</s>
<s>
Prior	O
to	O
the	O
release	O
of	O
Apple	B-Operating_System
DOS	I-Operating_System
3.1	O
,	O
Apple	O
users	O
had	O
to	O
rely	O
on	O
audio	B-Device
cassette	I-Device
tapes	I-Device
for	O
data	O
storage	O
and	O
retrieval	O
.	O
</s>
<s>
When	O
Apple	O
Computer	O
introduced	O
the	O
Apple	B-Device
II	I-Device
in	O
April	O
1977	O
,	O
the	O
new	O
computer	O
had	O
no	O
disk	O
drive	O
or	O
disk	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
(	O
DOS	O
)	O
.	O
</s>
<s>
Although	O
Apple	O
co-founder	O
Steve	O
Wozniak	O
designed	O
the	O
Disk	B-Device
II	I-Device
controller	O
late	O
that	O
year	O
,	O
and	O
believed	O
that	O
he	O
could	O
have	O
written	O
a	O
DOS	O
,	O
his	O
co-founder	O
Steve	O
Jobs	O
decided	O
to	O
outsource	O
the	O
task	O
.	O
</s>
<s>
The	O
company	O
considered	O
using	O
Digital	O
Research	O
's	O
CP/M	B-Application
,	O
but	O
Wozniak	O
sought	O
an	O
operating	B-General_Concept
system	I-General_Concept
that	O
was	O
easier	O
to	O
use	O
.	O
</s>
<s>
On	O
10	O
April	O
1978	O
Apple	O
signed	O
a	O
$	O
13,000	O
contract	O
with	O
Shepardson	B-Device
Microsystems	I-Device
to	O
write	O
a	O
DOS	O
and	O
deliver	O
it	O
within	O
35	O
days	O
.	O
</s>
<s>
Apple	O
provided	O
detailed	O
specifications	O
,	O
and	O
early	O
Apple	O
employee	O
Randy	O
Wigginton	O
worked	O
closely	O
with	O
Shepardson	O
's	O
Paul	O
Laughton	O
as	O
the	O
latter	O
wrote	O
the	O
operating	B-General_Concept
system	I-General_Concept
with	O
punched	B-Architecture
cards	I-Architecture
and	O
a	O
minicomputer	B-Architecture
.	O
</s>
<s>
There	O
was	O
no	O
Apple	B-Operating_System
DOS	I-Operating_System
1	O
or	O
2	O
.	O
</s>
<s>
Apple	B-Operating_System
DOS	I-Operating_System
3.0	O
,	O
a	O
renamed	O
issue	O
of	O
version	O
2.8	O
,	O
was	O
never	O
publicly	O
released	O
due	O
to	O
bugs	O
.	O
</s>
<s>
Apple	B-Operating_System
DOS	I-Operating_System
3.1	O
was	O
publicly	O
released	O
in	O
June	O
1978	O
,	O
slightly	O
more	O
than	O
one	O
year	O
after	O
the	O
Apple	B-Device
II	I-Device
was	O
introduced	O
,	O
becoming	O
the	O
first	O
disk-based	O
operating	B-General_Concept
system	I-General_Concept
for	O
any	O
Apple	O
computer	O
.	O
</s>
<s>
A	O
bug-fix	O
release	O
came	O
later	O
,	O
addressing	O
a	O
problem	O
by	O
means	O
of	O
its	O
utility	O
,	O
which	O
was	O
used	O
to	O
create	O
Apple	B-Operating_System
DOS	I-Operating_System
master	O
(	O
bootable	O
)	O
disks	O
:	O
The	O
built-in	O
command	O
created	O
disks	O
that	O
could	O
be	O
booted	O
only	O
on	O
machines	O
with	O
at	O
least	O
the	O
same	O
amount	O
of	O
memory	O
as	O
the	O
one	O
that	O
had	O
created	O
them	O
.	O
</s>
<s>
Apple	B-Operating_System
DOS	I-Operating_System
3.2	O
was	O
released	O
in	O
1979	O
to	O
reflect	O
changes	O
in	O
computer	O
booting	O
methods	O
that	O
were	O
built	O
into	O
the	O
successor	O
of	O
the	O
Apple	B-Device
II	I-Device
,	O
the	O
Apple	B-Device
II	I-Device
Plus	O
.	O
</s>
<s>
New	O
firmware	O
included	O
an	O
auto-start	O
feature	O
which	O
automatically	O
found	O
a	O
disk	O
controller	O
and	O
booted	O
from	O
it	O
when	O
the	O
system	O
was	O
powered	O
upearning	O
it	O
the	O
name	O
"	O
Autostart	O
ROM	B-Device
"	O
.	O
</s>
<s>
Apple	B-Operating_System
DOS	I-Operating_System
3.3	O
was	O
released	O
in	O
1980	O
.	O
</s>
<s>
It	O
improves	O
various	O
functions	O
of	O
release	O
3.2	O
,	O
while	O
allowing	O
for	O
large	O
gains	O
in	O
available	O
floppy	B-Device
disk	I-Device
storage	O
.	O
</s>
<s>
The	O
newer	O
P5A/P6A	O
PROMs	B-General_Concept
in	O
the	O
disk	O
controller	O
enable	O
the	O
reading	O
and	O
writing	O
of	O
data	O
at	O
a	O
higher	O
density	O
,	O
so	O
16	O
sectors	O
(	O
4KiB	O
)	O
can	O
be	O
stored	O
per	O
track	O
instead	O
of	O
13	O
sectors	O
(	O
3.25KiB	O
)	O
,	O
increasing	O
capacity	O
from	O
113.75KB	O
to	O
140KB	O
per	O
side	O
16KB	O
of	O
which	O
is	O
used	O
by	O
filesystem	B-Application
overhead	O
and	O
a	O
copy	O
of	O
DOS	O
,	O
leaving	O
124KB	O
for	O
user	O
programs	O
and	O
data	O
.	O
</s>
<s>
DOS	O
3.3	O
is	O
,	O
however	O
,	O
not	O
backward	B-General_Concept
compatible	I-General_Concept
;	O
it	O
cannot	O
read	O
or	O
write	O
DOS	O
3.2	O
disks	O
.	O
</s>
<s>
To	O
address	O
this	O
problem	O
,	O
Apple	O
Computer	O
released	O
"	O
MUFFIN	O
"	O
,	O
a	O
utility	O
to	O
migrate	O
Apple	B-Operating_System
DOS	I-Operating_System
3.2	O
files	O
and	O
programs	O
to	O
version	O
3.3	O
disks	O
.	O
</s>
<s>
To	O
migrate	O
Apple	B-Operating_System
DOS	I-Operating_System
3.3	O
files	O
back	O
to	O
version	O
3.2	O
disks	O
,	O
someone	O
wrote	O
a	O
"	O
NIFFUM	O
"	O
utility	O
.	O
</s>
<s>
There	O
are	O
also	O
commercial	O
utilities	O
(	O
such	O
as	O
Copy	O
II	O
Plus	O
)	O
that	O
can	O
copy	O
files	O
between	O
either	O
format	O
(	O
and	O
eventually	O
ProDOS	B-Operating_System
as	O
well	O
)	O
.	O
</s>
<s>
Release	O
3.3	O
also	O
improves	O
the	O
ability	O
to	O
switch	O
between	O
Integer	B-Language
BASIC	I-Language
and	O
Applesoft	B-Language
BASIC	I-Language
,	O
if	O
the	O
computer	O
has	O
a	O
language	O
card	O
(	O
RAM	B-Architecture
expansion	O
)	O
or	O
firmware	O
card	O
.	O
</s>
<s>
Apple	B-Operating_System
DOS	I-Operating_System
3.1	O
disks	O
use	O
13	O
sectors	O
of	O
data	O
per	O
track	O
,	O
each	O
sector	O
being	O
256	O
bytes	O
.	O
</s>
<s>
It	O
uses	O
35	O
tracks	O
per	O
disk	O
side	O
,	O
and	O
can	O
access	O
only	O
one	O
side	O
of	O
the	O
floppy	B-Device
disk	I-Device
,	O
unless	O
the	O
user	O
flipped	O
the	O
disk	O
over	O
.	O
</s>
<s>
The	O
first	O
layer	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
is	O
called	O
RWTS	O
,	O
which	O
stands	O
for	O
"	O
read/write	O
track	O
sector	O
"	O
.	O
</s>
<s>
An	O
API	B-Application
called	O
the	O
File	O
Manager	O
was	O
built	O
on	O
top	O
of	O
this	O
,	O
and	O
implements	O
functions	O
to	O
open	O
,	O
close	O
,	O
read	O
,	O
write	O
,	O
delete	O
,	O
lock	O
(	O
i.e.	O
</s>
<s>
There	O
is	O
also	O
a	O
function	O
,	O
for	O
listing	O
files	O
on	O
the	O
diskette	B-Device
,	O
and	O
an	O
function	O
,	O
which	O
formats	O
a	O
disk	O
for	O
use	O
with	O
DOS	O
,	O
storing	O
a	O
copy	O
of	O
DOS	O
on	O
the	O
first	O
three	O
tracks	O
,	O
and	O
storing	O
a	O
startup	O
program	O
(	O
usually	O
called	O
HELLO	O
)	O
that	O
is	O
auto-started	O
when	O
this	O
disk	O
is	O
booted	O
from	O
.	O
</s>
<s>
On	O
top	O
of	O
the	O
File	O
Manager	O
API	B-Application
,	O
the	O
main	O
DOS	O
routines	O
are	O
implemented	O
which	O
hook	O
into	O
the	O
machine	O
's	O
BASIC	O
interpreter	O
and	O
intercept	O
all	O
disk	O
commands	O
.	O
</s>
<s>
It	O
provides	O
BLOAD	B-Protocol
,	O
BSAVE	B-Protocol
,	O
and	O
BRUN	O
for	O
storing	O
,	O
loading	O
,	O
and	O
running	O
binary	O
executables	O
.	O
</s>
<s>
For	O
example	O
,	O
if	O
the	O
DOS	O
hooked	O
into	O
the	O
BASIC	O
CLI	B-Application
stops	O
functioning	O
,	O
it	O
can	O
be	O
reinitialized	O
by	O
calling	O
location	O
$03D0	O
(	O
976	O
)	O
hence	O
the	O
traditional	O
(	O
"	O
3D0	O
go	O
"	O
)	O
command	O
to	O
return	O
to	O
BASIC	O
from	O
the	O
System	O
Monitor	O
.	O
</s>
<s>
The	O
process	O
of	O
loading	O
Apple	B-Operating_System
DOS	I-Operating_System
involves	O
a	O
series	O
of	O
very	O
tiny	O
programs	O
,	O
each	O
of	O
which	O
carries	O
the	O
loading	O
process	O
forward	O
a	O
few	O
steps	O
before	O
passing	O
control	O
to	O
the	O
next	O
program	O
in	O
the	O
chain	O
.	O
</s>
<s>
Originally	O
,	O
the	O
Apple	B-Device
II	I-Device
ROM	B-Device
did	O
not	O
support	O
disk	O
booting	O
at	O
all	O
.	O
</s>
<s>
Both	O
the	O
Monitor	O
and	O
Integer	B-Language
BASIC	I-Language
have	O
commands	O
to	O
redirect	O
printing	O
to	O
a	O
printer	O
driver	O
in	O
a	O
designated	O
slot	O
,	O
so	O
the	O
conventional	O
way	O
to	O
boot	O
from	O
disk	O
then	O
was	O
to	O
command	O
the	O
computer	O
to	O
start	O
"	O
printing	O
"	O
to	O
the	O
disk	O
interface	O
card	O
,	O
typically	O
installed	O
in	O
slot	O
6	O
,	O
using	O
the	O
command	O
(	O
from	O
the	O
ML	O
monitor	O
)	O
or	O
(	O
from	O
BASIC	O
)	O
.	O
</s>
<s>
When	O
the	O
monitor	O
or	O
BASIC	O
issued	O
the	O
next	O
prompt	O
character	O
,	O
the	O
computer	O
would	O
call	O
the	O
ROM	B-Device
routines	O
on	O
the	O
disk	O
card	O
to	O
"	O
print	O
"	O
to	O
it	O
,	O
which	O
would	O
then	O
proceed	O
with	O
the	O
boot	O
sequence	O
.	O
</s>
<s>
When	O
the	O
Apple	B-Device
II	I-Device
Plus	O
was	O
introduced	O
,	O
it	O
included	O
the	O
ability	O
to	O
scan	O
each	O
expansion	O
slot	O
(	O
working	O
downward	O
from	O
slot	O
7	O
to	O
slot	O
1	O
)	O
for	O
a	O
bootable	O
expansion	O
card	O
ROM	B-Device
,	O
and	O
automatically	O
call	O
it	O
.	O
</s>
<s>
The	O
expansion	O
card	O
ROM	B-Device
boot	O
code	O
attempts	O
to	O
boot	O
from	O
drive	O
1	O
of	O
the	O
controller	O
by	O
moving	O
the	O
read/write	O
arm	O
to	O
track	O
zero	O
and	O
attempting	O
to	O
read	O
256	O
bytes	O
from	O
sector	O
zero	O
of	O
that	O
track	O
.	O
</s>
<s>
Sector	O
zero	O
contains	O
a	O
small	O
program	O
which	O
instructs	O
the	O
computer	O
to	O
read	O
sectors	O
0	O
through	O
9	O
of	O
track	O
zero	O
into	O
memory	O
using	O
part	O
of	O
the	O
ROM	B-Device
boot	O
code	O
(	O
rereading	O
sector	O
0	O
in	O
the	O
process	O
)	O
.	O
</s>
<s>
On	O
a	O
system	O
master	O
disk	O
,	O
code	O
is	O
also	O
included	O
to	O
determine	O
the	O
computer	O
's	O
RAM	B-Architecture
configuration	O
and	O
relocate	O
DOS	O
as	O
high	O
into	O
system	O
memory	O
as	O
possible	O
,	O
up	O
to	O
the	O
48KB	O
limit	O
of	O
the	O
Apple	B-Device
II	I-Device
's	O
main	O
memory	O
( $BFFF	O
)	O
.	O
</s>
<s>
The	O
appearance	O
of	O
the	O
right-hand	O
bracket	O
( ]	O
)	O
on	O
the	O
screen	O
is	O
an	O
indication	O
to	O
the	O
user	O
that	O
an	O
Applesoft	B-Language
BASIC	I-Language
startup	O
program	O
is	O
loading	O
,	O
while	O
a	O
greater-than	O
symbol	O
(	O
>	O
)	O
indicates	O
that	O
an	O
Integer	B-Language
BASIC	I-Language
program	O
is	O
loading	O
.	O
</s>
<s>
The	O
original	O
Apple	B-Device
II	I-Device
included	O
BASIC	O
interpreter	O
in	O
ROM	B-Device
known	O
originally	O
as	O
Apple	B-Language
BASIC	I-Language
and	O
later	O
as	O
Integer	B-Language
BASIC	I-Language
.	O
</s>
<s>
Variables	O
in	O
this	O
language	O
can	O
only	O
handle	O
integer	O
numbers	O
ranging	O
from	O
−	O
32,768	O
to	O
+	O
32,767	O
(	O
16-bit	B-Device
binary	O
values	O
)	O
;	O
floating	O
point	O
numbers	O
are	O
not	O
supported	O
.	O
</s>
<s>
Apple	O
commissioned	O
Microsoft	O
to	O
develop	O
Applesoft	B-Language
BASIC	I-Language
,	O
capable	O
of	O
handling	O
floating-point	O
numbers	O
.	O
</s>
<s>
Applesoft	B-Language
BASIC	I-Language
cannot	O
run	O
Integer	B-Language
BASIC	I-Language
programs	O
,	O
causing	O
some	O
users	O
to	O
resist	O
upgrading	O
to	O
it	O
.	O
</s>
<s>
DOS	O
3.3	O
was	O
released	O
when	O
Applesoft	B-Language
BASIC	I-Language
was	O
standard	O
in	O
ROM	B-Device
on	O
the	O
Apple	B-Device
II	I-Device
Plus	O
,	O
so	O
Apple	O
designed	O
it	O
to	O
support	O
switching	O
back	O
and	O
forth	O
between	O
the	O
two	O
BASIC	O
interpreters	O
.	O
</s>
<s>
Integer	B-Language
BASIC	I-Language
is	O
loaded	O
into	O
RAM	B-Architecture
on	O
the	O
language	O
card	O
of	O
Apple	B-Device
IIs	I-Device
(	O
if	O
present	O
)	O
and	O
by	O
typing	O
or	O
from	O
BASIC	O
,	O
the	O
user	O
can	O
switch	O
between	O
either	O
version	O
.	O
</s>
<s>
After	O
1980	O
,	O
Apple	B-Operating_System
DOS	I-Operating_System
entered	O
into	O
a	O
state	O
of	O
stagnation	O
as	O
Apple	O
concentrated	O
its	O
efforts	O
on	O
the	O
ill-fated	O
Apple	B-Device
III	I-Device
computer	O
and	O
its	O
SOS	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Two	O
more	O
versions	O
of	O
Apple	B-Operating_System
DOS	I-Operating_System
,	O
both	O
still	O
called	O
DOS	O
3.3	O
but	O
with	O
some	O
bug	O
fixes	O
and	O
better	O
support	O
for	O
the	O
new	O
Apple	B-Device
IIe	I-Device
model	O
,	O
were	O
released	O
in	O
early	O
and	O
mid-1983	O
.	O
</s>
<s>
Without	O
third-party	O
patches	O
,	O
Apple	B-Operating_System
DOS	I-Operating_System
can	O
only	O
read	O
floppy	B-Device
disks	I-Device
running	O
in	O
a	O
5.25-inch	O
Disk	B-Device
II	I-Device
drive	O
and	O
cannot	O
access	O
any	O
other	O
media	O
,	O
such	O
as	O
hard	O
disk	O
drives	O
,	O
virtual	O
RAM	B-Architecture
drives	O
,	O
or	O
3.5-inch	O
floppy	B-Device
disk	I-Device
drives	I-Device
.	O
</s>
<s>
The	O
structure	O
of	O
Apple	B-Operating_System
DOS	I-Operating_System
disks	O
(	O
particularly	O
the	O
free	O
sector	O
map	O
,	O
which	O
was	O
restricted	O
to	O
part	O
of	O
a	O
single	O
sector	O
)	O
is	O
such	O
that	O
it	O
is	O
not	O
possible	O
to	O
have	O
more	O
than	O
400KB	O
available	O
at	O
a	O
time	O
per	O
drive	O
without	O
a	O
major	O
rewrite	O
of	O
almost	O
all	O
sections	O
of	O
the	O
code	O
;	O
this	O
is	O
the	O
main	O
reason	O
Apple	O
abandoned	O
this	O
iteration	O
of	O
DOS	O
in	O
1983	O
,	O
when	O
Apple	B-Operating_System
DOS	I-Operating_System
was	O
entirely	O
replaced	O
by	O
ProDOS	B-Operating_System
.	O
</s>
<s>
ProDOS	B-Operating_System
retains	O
the	O
16-sector	O
low-level	O
format	O
of	O
DOS	O
3.3	O
for	O
5.25inch	O
disks	O
,	O
but	O
introduces	O
a	O
new	O
high-level	O
format	O
that	O
is	O
suitable	O
for	O
devices	O
of	O
up	O
to	O
32MB	O
;	O
this	O
makes	O
it	O
suitable	O
for	O
hard	O
disks	O
from	O
that	O
era	O
and	O
3.5-inch	O
floppies	B-Device
.	O
</s>
<s>
All	O
the	O
Apple	O
computers	O
from	O
the	O
II	O
Plus	O
onward	O
can	O
run	O
both	O
DOS	O
3.3	O
and	O
ProDOS	B-Operating_System
,	O
the	O
Plus	O
requiring	O
a	O
"	O
Language	O
Card	O
"	O
memory	O
expansion	O
to	O
use	O
ProDOS	B-Operating_System
;	O
the	O
e	O
and	O
later	O
models	O
have	O
built-in	O
Language	O
Card	O
hardware	O
,	O
and	O
so	O
can	O
run	O
ProDOS	B-Operating_System
straight	O
.	O
</s>
<s>
ProDOS	B-Operating_System
includes	O
software	O
to	O
copy	O
files	O
from	O
Apple	B-Operating_System
DOS	I-Operating_System
disks	O
.	O
</s>
<s>
However	O
,	O
many	O
people	O
who	O
had	O
no	O
need	O
for	O
the	O
improvements	O
of	O
ProDOS	B-Operating_System
(	O
and	O
who	O
did	O
not	O
like	O
its	O
much	O
higher	O
memory	O
footprint	O
)	O
continued	O
using	O
Apple	B-Operating_System
DOS	I-Operating_System
or	O
one	O
of	O
its	O
clones	B-General_Concept
long	O
after	O
1983	O
.	O
</s>
<s>
The	O
Apple	O
convention	O
of	O
storing	O
a	O
bootable	O
OS	O
on	O
every	O
single	O
floppy	B-Device
disk	I-Device
means	O
that	O
commercial	O
software	O
can	O
be	O
used	O
no	O
matter	O
what	O
OS	O
the	O
user	O
owns	O
.	O
</s>
<s>
A	O
program	O
called	O
DOS.MASTER	O
enables	O
users	O
to	O
have	O
multiple	O
virtual	O
DOS	O
3.3	O
partitions	O
on	O
a	O
larger	O
ProDOS	B-Operating_System
volume	O
,	O
which	O
allows	O
the	O
use	O
of	O
many	O
floppy-based	O
DOS	O
programs	O
with	O
a	O
hard	O
disk	O
.	O
</s>
<s>
Shortly	O
after	O
ProDOS	B-Operating_System
came	O
out	O
,	O
Apple	O
withdrew	O
permission	O
from	O
third	O
parties	O
to	O
redistribute	O
DOS	O
3.3	O
,	O
but	O
granted	O
one	O
company	O
,	O
Syndicomm	O
,	O
an	O
exclusive	O
license	O
to	O
resell	O
DOS	O
3.3	O
.	O
</s>
<s>
Commercial	O
games	O
usually	O
did	O
not	O
use	O
Apple	B-Operating_System
DOS	I-Operating_System
,	O
instead	O
having	O
their	O
own	O
custom	O
disk	O
routines	O
for	O
copy	O
protection	O
purposes	O
as	O
well	O
as	O
for	O
performance	O
.	O
</s>
<s>
Later	O
,	O
ProDOS	B-Operating_System
arranged	O
the	O
sectors	O
in	O
this	O
order	O
:	O
</s>
<s>
This	O
functionality	O
soon	O
appeared	O
in	O
commercial	O
products	O
,	O
such	O
as	O
Pronto-DOS	O
,	O
Diversi-DOS	O
,	O
Hyper-DOS	O
,	O
and	O
David-DOS	O
,	O
along	O
with	O
additional	O
features	O
,	O
but	O
it	O
was	O
never	O
used	O
in	O
an	O
official	O
Apple	B-Operating_System
DOS	I-Operating_System
release	O
.	O
</s>
<s>
Similar	O
functionality	O
was	O
,	O
however	O
,	O
employed	O
by	O
Apple	O
's	O
successor	O
operating	B-General_Concept
system	I-General_Concept
,	O
ProDOS	B-Operating_System
.	O
</s>
<s>
The	O
Apple	O
IIGS-specific	O
operating	B-General_Concept
system	I-General_Concept
GS/OS	B-Application
would	O
eventually	O
employ	O
an	O
even	O
more	O
efficient	O
"	O
scatter	O
read	O
"	O
technique	O
that	O
would	O
read	O
any	O
sector	O
that	O
happened	O
to	O
be	O
passing	O
under	O
the	O
read	O
head	O
if	O
it	O
was	O
needed	O
for	O
the	O
file	O
being	O
read	O
.	O
</s>
<s>
In	O
2013	O
,	O
more	O
than	O
35	O
years	O
after	O
the	O
Apple	B-Device
II	I-Device
debuted	O
,	O
the	O
original	O
Apple	B-Operating_System
DOS	I-Operating_System
source	O
code	O
was	O
released	O
by	O
the	O
Computer	O
History	O
Museum	O
on	O
its	O
website	O
.	O
</s>
