<s>
A	O
disk	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
(	O
DOS	O
)	O
is	O
a	O
computer	B-General_Concept
operating	I-General_Concept
system	I-General_Concept
that	O
resides	O
on	O
and	O
can	O
use	O
a	O
disk	B-Device
storage	I-Device
device	O
,	O
such	O
as	O
a	O
floppy	B-Device
disk	I-Device
,	O
hard	B-Device
disk	I-Device
drive	I-Device
,	O
or	O
optical	B-Device
disc	I-Device
.	O
</s>
<s>
A	O
disk	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
provides	O
a	O
file	B-Application
system	I-Application
for	O
organizing	O
,	O
reading	O
,	O
and	O
writing	O
files	B-Operating_System
on	O
the	O
storage	O
disk	B-Device
.	O
</s>
<s>
Strictly	O
,	O
this	O
definition	O
does	O
not	O
include	O
any	O
other	O
functionality	O
,	O
so	O
it	O
does	O
not	O
apply	O
to	O
more	O
complex	O
OSes	O
,	O
such	O
as	O
Microsoft	B-Application
Windows	I-Application
,	O
and	O
is	O
more	O
appropriately	O
used	O
only	O
for	O
older	O
generations	O
of	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
Disk	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
for	O
mainframes	B-Architecture
,	O
minicomputers	B-Architecture
,	O
microprocessors	B-Architecture
,	O
and	O
home	O
computers	O
are	O
usually	O
loaded	O
from	O
the	O
disks	B-Device
as	O
part	O
of	O
the	O
boot	B-Operating_System
process	I-Operating_System
.	O
</s>
<s>
Early	O
computers	O
predate	O
disk	B-Device
drives	I-Device
,	O
floppy	B-Device
disks	I-Device
,	O
or	O
modern	O
flash	B-Device
storage	I-Device
.	O
</s>
<s>
Early	O
storage	O
devices	O
such	O
as	O
delay	O
lines	O
,	O
core	B-General_Concept
memories	I-General_Concept
,	O
punched	B-Architecture
cards	I-Architecture
,	O
punched	O
tape	O
,	O
magnetic	O
tape	O
,	O
and	O
magnetic	B-General_Concept
drums	I-General_Concept
are	O
used	O
instead	O
.	O
</s>
<s>
Early	O
microcomputers	O
and	O
home	O
computers	O
use	O
paper	O
tape	O
,	O
audio	B-Device
cassette	I-Device
tape	I-Device
(	O
such	O
as	O
Kansas	B-Device
City	I-Device
standard	I-Device
)	O
,	O
or	O
nothing	O
.	O
</s>
<s>
Without	O
permanent	O
storage	O
,	O
program	O
and	O
data	O
entry	O
is	O
done	O
at	O
front	B-Device
panel	I-Device
switches	O
directly	O
into	O
memory	O
or	O
through	O
a	O
computer	B-General_Concept
terminal	I-General_Concept
or	O
keyboard	O
,	O
sometimes	O
controlled	O
by	O
a	O
BASIC	O
interpreter	O
in	O
ROM	B-Device
.	O
</s>
<s>
In	O
the	O
early	O
1960s	O
,	O
as	O
disk	B-Device
drives	I-Device
became	O
larger	O
and	O
more	O
affordable	O
,	O
various	O
mainframe	B-Architecture
and	O
minicomputer	B-Architecture
vendors	O
introduced	O
disk	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
and	O
modified	O
existing	O
operating	B-General_Concept
systems	I-General_Concept
to	O
use	O
disks	B-Device
.	O
</s>
<s>
Hard	B-Device
disks	I-Device
and	O
floppy	B-Device
disk	I-Device
drives	I-Device
require	O
software	O
to	O
manage	O
rapid	O
access	O
to	O
block	O
storage	O
of	O
sequential	O
and	O
other	O
data	O
.	O
</s>
<s>
For	O
most	O
microcomputers	O
,	O
a	O
disk	B-Device
drive	I-Device
of	O
any	O
kind	O
was	O
an	O
optional	O
peripheral	O
.	O
</s>
<s>
The	O
disk	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
component	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
was	O
only	O
needed	O
when	O
a	O
disk	B-Device
drive	I-Device
was	O
used	O
.	O
</s>
<s>
By	O
the	O
time	O
IBM	O
announced	O
the	O
System/360	B-Application
mainframes	B-Architecture
,	O
the	O
concept	O
of	O
a	O
disk	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
was	O
well	O
established	O
.	O
</s>
<s>
Although	O
IBM	O
did	O
offer	O
Basic	B-Application
Programming	I-Application
Support	I-Application
(	O
BPS/360	B-Application
)	O
and	O
TOS/360	B-Application
for	O
small	O
systems	O
,	O
they	O
were	O
out	O
of	O
the	O
mainstream	O
and	O
most	O
customers	O
used	O
either	O
DOS/360	O
or	O
OS/360	O
.	O
</s>
<s>
Most	O
home	O
and	O
personal	O
computers	O
of	O
the	O
late	O
1970s	O
and	O
1980s	O
used	O
a	O
disk	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
,	O
most	O
often	O
with	O
"	O
DOS	O
"	O
in	O
the	O
name	O
and	O
simply	O
referred	O
to	O
as	O
"	O
DOS	O
"	O
within	O
their	O
respective	O
communities	O
:	O
CBM	B-Device
DOS	I-Device
for	O
Commodore	O
8-bit	O
systems	O
,	O
Atari	B-Operating_System
DOS	I-Operating_System
for	O
the	O
Atari	B-Device
8-bit	I-Device
family	I-Device
,	O
TRS-DOS	B-Operating_System
for	O
the	O
TRS-80	B-Device
,	O
Apple	B-Operating_System
DOS	I-Operating_System
and	O
ProDOS	B-Operating_System
for	O
the	O
Apple	O
II	O
,	O
and	O
MS-DOS	B-Application
for	O
IBM	B-Device
PC	I-Device
compatibles	O
.	O
</s>
<s>
Usually	O
,	O
a	O
disk	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
was	O
loaded	O
from	O
a	O
disk	B-Device
.	O
</s>
<s>
Among	O
the	O
exceptions	O
were	O
Commodore	O
,	O
whose	O
DOS	O
resided	O
on	O
ROM	B-Device
chips	I-Device
in	O
the	O
disk	B-Device
drives	I-Device
.	O
</s>
<s>
The	O
Lt	B-Device
.	I-Device
Kernal	I-Device
hard	B-Device
disk	I-Device
subsystem	O
for	O
the	O
Commodore	O
64	O
and	O
Commodore	B-Device
128	I-Device
models	O
stored	O
its	O
DOS	O
on	O
the	O
disk	B-Device
,	O
as	O
is	O
the	O
case	O
with	O
modern	O
systems	O
,	O
and	O
loaded	O
the	O
DOS	O
into	O
RAM	B-Architecture
at	O
boot	B-Operating_System
time	I-Operating_System
;	O
AmigaDOS	O
also	O
mostly	O
resided	O
in	O
ROM	B-Device
as	O
a	O
part	O
of	O
a	O
Kickstart	B-Device
firmware	O
,	O
but	O
a	O
few	O
select	O
versions	O
were	O
also	O
loaded	O
from	O
disk	B-Device
;	O
the	O
British	O
BBC	B-Device
Micro	I-Device
's	O
optional	O
Disc	B-Application
Filing	I-Application
System	I-Application
,	O
DFS	O
,	O
offered	O
as	O
a	O
kit	O
with	O
a	O
disk	B-Device
controller	O
chip	O
,	O
a	O
ROM	B-Device
chip	I-Device
,	O
and	O
few	O
logic	O
chips	O
,	O
to	O
be	O
installed	O
inside	O
the	O
computer	O
.	O
</s>
<s>
Apple	B-Operating_System
DOS	I-Operating_System
is	O
the	O
primary	O
operating	B-General_Concept
system	I-General_Concept
for	O
the	O
Apple	B-Device
II	I-Device
series	I-Device
of	O
computers	O
,	O
from	O
1979	O
with	O
the	O
introduction	O
of	O
the	O
floppy	B-Device
disk	I-Device
drive	I-Device
,	O
until	O
1983	O
when	O
it	O
was	O
replaced	O
by	O
ProDOS	B-Operating_System
.	O
</s>
<s>
Commodore	B-Device
DOS	I-Device
is	O
on	O
8-bit	O
Commodore	O
computers	O
such	O
as	O
the	O
Commodore	O
64	O
.	O
</s>
<s>
Unlike	O
most	O
other	O
DOS	O
systems	O
,	O
it	O
is	O
integrated	O
into	O
the	O
disk	B-Device
drives	I-Device
,	O
not	O
loaded	O
into	O
the	O
computer	O
's	O
own	O
memory	O
.	O
</s>
<s>
Atari	B-Operating_System
DOS	I-Operating_System
is	O
used	O
by	O
the	O
Atari	B-Device
8-bit	I-Device
family	I-Device
of	O
computers	O
.	O
</s>
<s>
The	O
Atari	O
OS	O
only	O
offers	O
low-level	O
disk-access	O
,	O
so	O
an	O
extra	O
layer	O
called	O
DOS	O
can	O
be	O
booted	O
from	O
a	O
floppy	B-Device
for	O
higher	O
level	O
functions	O
such	O
as	O
filesystems	B-Application
.	O
</s>
<s>
Third-party	O
replacements	O
for	O
Atari	B-Operating_System
DOS	I-Operating_System
include	O
DOS	B-Application
XL	I-Application
,	O
SpartaDOS	B-Operating_System
,	O
MyDOS	O
,	O
TurboDOS	B-Operating_System
,	O
and	O
Top-DOS	O
.	O
</s>
<s>
MSX-DOS	B-Operating_System
is	O
for	O
the	O
MSX	B-Operating_System
computer	O
standard	O
.	O
</s>
<s>
The	O
initial	O
version	O
,	O
released	O
in	O
1984	O
,	O
is	O
MS-DOS	B-Application
1.0	O
ported	O
to	O
Z80	B-General_Concept
.	O
</s>
<s>
The	O
MSX-DOS	B-Operating_System
kernel	O
resides	O
in	O
ROM	B-Device
(	O
built-in	O
on	O
the	O
disk	B-Device
controller	O
)	O
so	O
basic	O
file	B-Application
access	I-Application
capacity	O
is	O
available	O
even	O
without	O
the	O
command	O
interpreter	O
,	O
by	O
using	O
BASIC	O
extended	O
commands	O
.	O
</s>
<s>
Disc	B-Application
Filing	I-Application
System	I-Application
(	O
DFS	O
)	O
is	O
an	O
optional	O
component	O
for	O
the	O
Acorn	B-Device
BBC	I-Device
Micro	I-Device
,	O
as	O
a	O
kit	O
with	O
a	O
disk	B-Device
controller	O
chip	O
,	O
a	O
ROM	B-Device
chip	I-Device
,	O
and	O
a	O
few	O
logic	O
chips	O
,	O
to	O
be	O
installed	O
inside	O
the	O
computer	O
.	O
</s>
<s>
Advanced	B-Device
Disc	I-Device
Filing	I-Device
System	I-Device
(	O
ADFS	O
)	O
is	O
a	O
successor	O
to	O
Acorn	O
's	O
DFS	O
.	O
</s>
<s>
AMSDOS	B-Operating_System
is	O
for	O
the	O
Amstrad	B-Device
CPC	I-Device
computers	O
.	O
</s>
<s>
GDOS	O
and	O
G+DOS	O
is	O
for	O
the	O
+D	B-Device
and	O
DISCiPLE	B-Device
disk	B-Device
interfaces	O
for	O
the	O
ZX	B-Operating_System
Spectrum	I-Operating_System
.	O
</s>
<s>
Some	O
disk	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
are	O
the	O
operating	B-General_Concept
systems	I-General_Concept
for	O
the	O
entire	O
computer	O
system	O
.	O
</s>
<s>
The	O
Burroughs	O
(	O
now	O
Unisys	O
)	O
Master	B-Application
Control	I-Application
Program	I-Application
(	O
MCP	B-Application
)	O
for	O
the	O
B5000	B-Device
originally	O
runs	O
from	O
a	O
drum	O
,	O
but	O
starting	O
with	O
the	O
B5500	O
it	O
runs	O
from	O
a	O
disk	B-Device
.	O
</s>
<s>
It	O
is	O
the	O
basis	O
for	O
the	O
MCP	B-Application
on	O
the	O
B6500	O
,	O
B7500	O
,	O
and	O
successors	O
.	O
</s>
<s>
The	O
SIPROS	O
,	O
Chippewa	B-Operating_System
Operating	I-Operating_System
System	I-Operating_System
(	O
COS	O
)	O
,	O
SCOPE	B-Operating_System
,	O
MACE	O
and	O
KRONOS	B-Operating_System
operating	B-General_Concept
systems	I-General_Concept
on	O
the	O
Control	O
Data	O
Corporation	O
(	O
CDC	O
)	O
6000	B-Device
series	I-Device
and	O
7600	B-Device
are	O
all	O
disk	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
.	O
</s>
<s>
KRONOS	B-Operating_System
became	O
NOS	B-Operating_System
and	O
SCOPE	B-Operating_System
became	O
NOS/BE	B-Operating_System
.	O
</s>
<s>
The	O
GECOS	B-Application
operating	B-General_Concept
system	I-General_Concept
for	O
the	O
GE	O
(	O
later	O
Honeywell	O
and	O
Groupe	O
Bull	O
)	O
600	B-Device
family	O
of	O
mainframe	B-Architecture
computers	I-Architecture
(	O
it	O
later	O
became	O
GCOS	B-Application
)	O
.	O
</s>
<s>
The	O
IBM	B-Application
Basic	I-Application
Operating	I-Application
System/360	I-Application
(	O
BOS/360	B-Application
)	O
,	O
Disk	B-Application
Operating	I-Application
System/360	I-Application
(	O
DOS/360	O
)	O
and	O
Operating	O
System/360	B-Application
(	O
OS/360	O
)	O
are	O
standard	O
for	O
all	O
but	O
the	O
smallest	O
System/360	B-Application
installations	O
;	O
the	O
360/67	B-Device
also	O
has	O
Control	O
Program-67	O
/Cambridge	O
Monitor	O
System	O
(	O
CP-67/CMS	O
)	O
and	O
Time	O
Sharing	O
System/360	B-Application
(	O
TSS/360	B-Application
)	O
.	O
</s>
<s>
BOS	O
is	O
gone	O
,	O
CP-67/CMS	O
has	O
evolved	O
into	O
z/VM	B-Application
,	O
DOS	O
has	O
evolved	O
into	O
z/VSE	B-Application
,	O
OS	O
has	O
evolved	O
into	O
z/OS	B-Application
and	O
TSS/360	B-Application
evolved	O
into	O
TSS/370	B-Application
PRPQ	O
,	O
which	O
is	O
now	O
gone	O
..	O
</s>
<s>
The	O
DOS-11	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
for	O
DEC	B-Device
PDP-11	I-Device
minicomputers	B-Architecture
.	O
</s>
<s>
CP/M	B-Application
is	O
a	O
disk	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
,	O
as	O
the	O
main	O
or	O
alternate	O
operating	B-General_Concept
system	I-General_Concept
for	O
numerous	O
microcomputers	O
of	O
the	O
1970s	O
and	O
1980s	O
.	O
</s>
<s>
TRSDOS	B-Operating_System
is	O
the	O
operating	B-General_Concept
system	I-General_Concept
for	O
the	O
TRS-80	B-Device
line	O
of	O
computers	O
from	O
Tandy	O
.	O
</s>
<s>
MS-DOS	B-Application
for	O
IBM	B-Device
PC	I-Device
compatibles	O
with	O
Intel	B-Operating_System
x86	I-Operating_System
CPUs	O
.	O
</s>
<s>
86-DOS	B-Operating_System
was	O
modeled	O
on	O
CP/M	B-Application
,	O
and	O
then	O
was	O
adapted	O
as	O
the	O
basis	O
for	O
Microsoft	O
's	O
MS-DOS	B-Application
.	O
</s>
<s>
It	O
was	O
rebranded	O
by	O
IBM	O
as	O
PC	B-Operating_System
DOS	I-Operating_System
until	O
1993	O
.	O
</s>
<s>
Various	O
compatible	O
systems	O
were	O
later	O
produced	O
by	O
different	O
organizations	O
,	O
starting	O
with	O
DR-DOS	B-Application
in	O
1988	O
.	O
</s>
