<s>
Many	O
early	O
microcomputer	B-Architecture
and	O
home	O
computer	O
systems	O
used	O
cassette	B-Device
tapes	I-Device
as	O
an	O
inexpensive	O
magnetic	B-Architecture
tape	I-Architecture
data	I-Architecture
storage	I-Architecture
system	O
.	O
</s>
<s>
The	O
main	O
exception	O
to	O
this	O
rule	O
was	O
the	O
Kansas	B-Device
City	I-Device
standard	I-Device
,	O
which	O
was	O
supported	O
by	O
most	O
S-100	B-Architecture
bus	I-Architecture
based	O
computers	O
and	O
was	O
later	O
adopted	O
by	O
a	O
few	O
other	O
vendors	O
like	O
the	O
BBC	B-Device
Computer	I-Device
and	O
MSX	B-Operating_System
.	O
</s>
<s>
One	O
of	O
the	O
earliest	O
efforts	O
to	O
develop	O
a	O
microcomputer	B-Architecture
for	O
home	O
use	O
was	O
carried	O
out	O
in	O
the	O
early	O
1970s	O
at	O
RCA	O
and	O
led	O
to	O
the	O
COSMAC	B-General_Concept
processor	O
design	O
.	O
</s>
<s>
Bytes	O
were	O
written	O
with	O
a	O
single	O
mark	O
bit	O
,	O
eight	O
data	O
bits	O
,	O
and	O
a	O
final	O
odd	B-Error_Name
parity	I-Error_Name
bit	O
.	O
</s>
<s>
There	O
was	O
no	O
support	O
for	O
reading	O
and	O
writing	O
the	O
data	O
in	O
the	O
basic	O
operating	B-General_Concept
system	I-General_Concept
;	O
users	O
had	O
to	O
type	O
in	O
their	O
own	O
loader	B-Operating_System
program	I-Operating_System
to	O
do	O
so	O
,	O
although	O
the	O
hexadecimal	O
example	O
version	O
of	O
the	O
code	O
was	O
provided	O
and	O
is	O
quite	O
small	O
.	O
</s>
<s>
In	O
contrast	O
to	O
almost	O
every	O
other	O
system	O
of	O
the	O
era	O
,	O
HITS	O
did	O
not	O
use	O
FSK	O
for	O
its	O
storage	O
mechanism	O
;	O
instead	O
it	O
used	O
pulse-width	B-Algorithm
modulation	I-Algorithm
,	O
or	O
PWM	O
.	O
</s>
<s>
Assembler	B-Language
code	I-Language
programs	O
for	O
reading	O
and	O
writing	O
on	O
Intel	B-General_Concept
8080	I-General_Concept
machines	O
were	O
provided	O
.	O
</s>
<s>
The	O
Kansas	B-Device
City	I-Device
Standard	I-Device
(	O
KCS	B-Device
)	O
was	O
one	O
of	O
the	O
few	O
cassette	O
formats	O
that	O
was	O
standardized	O
to	O
any	O
degree	O
.	O
</s>
<s>
It	O
was	O
created	O
by	O
a	O
group	O
of	O
S-100	B-Architecture
bus	I-Architecture
manufacturers	O
at	O
a	O
meeting	O
hosted	O
by	O
Byte	O
Magazine	O
in	O
November	O
1975	O
in	O
Kansas	O
City	O
.	O
</s>
<s>
KCS	B-Device
was	O
a	O
simple	O
FSK	O
system	O
that	O
recorded	O
zeros	O
as	O
four	O
cycles	O
of	O
a	O
1200Hz	O
tone	O
and	O
ones	O
as	O
eight	O
cycles	O
of	O
2400Hz	O
.	O
</s>
<s>
Data	O
was	O
recorded	O
in	O
eight-bit	O
bytes	O
,	O
least	O
significant	O
bit	O
first	O
,	O
with	O
a	O
parity	B-Error_Name
bit	I-Error_Name
added	O
to	O
seven-bit	O
data	O
if	O
needed	O
.	O
</s>
<s>
If	O
shorter	O
data	O
was	O
being	O
written	O
,	O
for	O
instance	O
,	O
six-bit	O
ASCII	B-Protocol
codes	I-Protocol
,	O
any	O
unused	O
bits	O
were	O
filled	O
with	O
mark	O
at	O
the	O
end	O
to	O
fill	O
out	O
eight	O
bits	O
.	O
</s>
<s>
The	O
data	O
was	O
written	O
using	O
a	O
slightly	O
modified	O
version	O
of	O
Manchester	B-Protocol
encoding	I-Protocol
.	O
</s>
<s>
CUTS	O
was	O
a	O
faster	O
version	O
of	O
the	O
KCS	B-Device
system	O
,	O
developed	O
by	O
Processor	O
Technology	O
.	O
</s>
<s>
This	O
made	O
the	O
effective	O
data	O
rate	O
1200bit/s	O
,	O
four	O
times	O
that	O
of	O
the	O
KCS	B-Device
version	O
.	O
</s>
<s>
The	O
CUTS	O
S-100	O
board	O
could	O
support	O
either	O
CUTS	O
or	O
KCS	B-Device
for	O
reading	O
and	O
writing	O
and	O
could	O
support	O
two	O
tape	O
decks	O
from	O
a	O
single	O
board	O
.	O
</s>
<s>
Acorn	O
Computers	O
Ltd	O
implemented	O
both	O
the	O
original	O
300-baud	O
KCS	B-Device
and	O
the	O
1200-baud	O
CUTS	O
variation	O
in	O
their	O
BBC	B-Device
Micro	I-Device
and	O
Acorn	B-Device
Electron	I-Device
.	O
</s>
<s>
MSX	B-Operating_System
took	O
this	O
another	O
step	O
to	O
2400bit/s	O
by	O
moving	O
to	O
higher	O
frequencies	O
,	O
using	O
a	O
single	O
2400Hz	O
cycle	O
for	O
a	O
space	O
and	O
two	O
cycles	O
of	O
4800Hz	O
for	O
a	O
mark	O
.	O
</s>
<s>
Additionally	O
,	O
MSX	B-Operating_System
defined	O
a	O
block-based	O
file	O
format	O
,	O
although	O
it	O
changed	O
several	O
times	O
.	O
</s>
<s>
Blocks	O
could	O
contain	O
between	O
0	O
and	O
255	O
bytes	O
of	O
data	O
with	O
header	O
information	O
and	O
a	O
one-byte	O
checksum	B-Algorithm
,	O
later	O
changing	O
to	O
a	O
16-bit	O
cyclic	O
redundancy	O
check	O
(	O
CRC	O
)	O
.	O
</s>
<s>
The	O
concept	O
was	O
then	O
picked	O
up	O
by	O
Daniel	O
Meyer	O
and	O
Gary	O
Kay	O
of	O
Southwest	O
Technical	O
Products	O
(	O
SWTPC	O
)	O
,	O
who	O
arranged	O
for	O
Robert	O
Uiterwyk	O
to	O
provide	O
his	O
4K	O
BASIC	O
interpreter	O
program	O
for	O
the	O
Motorola	B-Device
6800	I-Device
in	O
KCS	B-Device
format	O
.	O
</s>
<s>
The	O
May	O
1977	O
issue	O
of	O
Interface	O
Age	O
contains	O
the	O
first	O
"	O
Floppy	O
ROM	O
"	O
,	O
a	O
33	O
RPM	O
record	O
containing	O
about	O
six	O
minutes	O
of	O
Kansas	B-Device
City	I-Device
standard	I-Device
audio	O
.	O
</s>
<s>
In	O
this	O
case	O
,	O
a	O
five-second	O
header	O
and	O
footer	O
of	O
the	O
2400Hz	O
signal	O
was	O
added	O
to	O
the	O
file	O
,	O
and	O
the	O
program	O
was	O
sent	O
as	O
a	O
single	O
long	O
series	O
of	O
ASCII	B-Protocol
bytes	O
.	O
</s>
<s>
The	O
bytes	O
were	O
sent	O
with	O
a	O
single	O
mark	O
start	O
bit	O
,	O
eight	O
bits	O
of	O
data	O
containing	O
a	O
seven-bit	B-Protocol
ASCII	I-Protocol
code	O
with	O
the	O
most	O
significant	O
bit	O
set	O
to	O
1	O
,	O
and	O
a	O
single	O
mark	O
stop	O
bit	O
.	O
</s>
<s>
The	O
Apple	B-Device
I	I-Device
introduced	O
an	O
expansion-card	O
based	O
cassette	O
system	O
similar	O
to	O
KCS	B-Device
,	O
recording	O
a	O
single	O
cycle	O
of	O
2000Hz	O
for	O
a	O
space	O
and	O
a	O
single	O
cycle	O
of	O
1000Hz	O
for	O
a	O
mark	O
.	O
</s>
<s>
The	O
associated	O
device	B-Application
driver	I-Application
in	O
PROM	O
offered	O
an	O
interactive	O
mode	O
that	O
allowed	O
users	O
to	O
write	O
memory	O
locations	O
to	O
tape	O
.	O
</s>
<s>
The	O
Apple	B-Device
II	I-Device
moved	O
the	O
cassette	O
interface	O
onto	O
the	O
motherboard	O
and	O
made	O
several	O
changes	O
to	O
the	O
format	O
.	O
</s>
<s>
Data	O
following	O
the	O
header	O
was	O
recoded	O
as	O
before	O
,	O
but	O
was	O
also	O
appended	O
with	O
an	O
8-bit	O
checksum	B-Algorithm
.	O
</s>
<s>
Applesoft	B-Language
BASIC	I-Language
saved	O
user	O
programs	O
as	O
two	O
"	O
records	O
"	O
,	O
the	O
first	O
consisting	O
of	O
the	O
header	O
signal	O
followed	O
by	O
the	O
program	O
length	O
and	O
checksum	B-Algorithm
and	O
the	O
second	O
with	O
the	O
header	O
signal	O
,	O
program	O
data	O
and	O
checksum	B-Algorithm
.	O
</s>
<s>
The	O
format	O
for	O
the	O
TI-99/4	B-Device
was	O
driven	O
by	O
internal	O
I/O	O
pins	O
being	O
toggled	O
at	O
the	O
rate	O
needed	O
to	O
produce	O
the	O
proper	O
tones	O
on	O
the	O
cassette	O
.	O
</s>
<s>
The	O
data	O
was	O
encoded	O
in	O
blocks	O
;	O
these	O
started	O
with	O
8-byte	O
lead-in	O
of	O
spaces	O
and	O
a	O
single	O
mark	O
,	O
then	O
64	O
bytes	O
of	O
data	O
,	O
and	O
finally	O
a	O
1-byte	O
checksum	B-Algorithm
,	O
for	O
a	O
total	O
length	O
of	O
73	O
bytes	O
.	O
</s>
<s>
The	O
Commodore	O
tape	O
format	O
,	O
introduced	O
on	O
the	O
Commodore	B-Device
PET	I-Device
,	O
uses	O
a	O
combination	O
of	O
FSK	O
and	O
PWM	O
methodology	O
.	O
</s>
<s>
The	O
primary	O
use	O
of	O
the	O
system	O
was	O
with	O
Commodore	B-Language
BASIC	I-Language
,	O
which	O
recorded	O
a	O
header	O
containing	O
a	O
series	O
of	O
bytes	O
used	O
as	O
a	O
way	O
for	O
the	O
system	O
to	O
track	O
the	O
tape	O
speed	O
,	O
followed	O
by	O
the	O
file	O
name	O
,	O
size	O
and	O
other	O
data	O
.	O
</s>
<s>
It	O
was	O
possible	O
to	O
bypass	O
the	O
Commodore	O
tape	O
format	O
routines	O
and	O
access	O
the	O
I/O	O
hardware	O
directly	O
,	O
which	O
allowed	O
for	O
the	O
widespread	O
development	O
of	O
'	O
turbo	O
 '	O
loaders	B-Operating_System
for	O
Commodore	O
computers	O
.	O
</s>
<s>
The	O
Atari	B-Device
8-bit	I-Device
family	I-Device
used	O
a	O
system	O
that	O
was	O
based	O
on	O
consultations	O
with	O
recording	O
engineers	O
,	O
one	O
of	O
the	O
most	O
obvious	O
outcomes	O
being	O
to	O
use	O
two	O
frequencies	O
that	O
were	O
not	O
harmonics	O
of	O
each	O
other	O
.	O
</s>
<s>
The	O
operating	B-General_Concept
system	I-General_Concept
defined	O
a	O
packet-oriented	O
file	O
format	O
with	O
128	O
bytes	O
of	O
payload	O
with	O
two	O
header	O
bytes	O
,	O
a	O
control	O
byte	O
,	O
and	O
a	O
following	O
checksum	B-Algorithm
,	O
making	O
the	O
packet	O
a	O
total	O
of	O
132	O
bytes	O
long	O
.	O
</s>
<s>
The	O
control	O
byte	O
had	O
three	O
values	O
:	O
$FC	O
was	O
a	O
full-length	O
packet	O
,	O
$FA	O
was	O
a	O
short	O
packet	O
with	O
the	O
length	O
stored	O
prior	O
to	O
the	O
checksum	B-Algorithm
,	O
and	O
finally	O
$FE	O
was	O
the	O
end-of-file	O
(	O
EOF	O
)	O
marker	O
.	O
</s>
<s>
For	O
other	O
uses	O
,	O
like	O
a	O
BASIC	B-Language
programming	I-Language
language	I-Language
program	O
in	O
text	O
format	O
that	O
had	O
to	O
be	O
converted	O
line	O
by	O
line	O
to	O
the	O
internal	O
binary	O
format	O
,	O
the	O
normal	O
IRG	O
was	O
used	O
,	O
3seconds	O
.	O
</s>
