<s>
Punter	B-Protocol
is	O
a	O
protocol	B-Protocol
for	I-Protocol
file	I-Protocol
transfer	I-Protocol
developed	O
in	O
the	O
1980s	O
by	O
Steve	O
Punter	B-Protocol
.	O
</s>
<s>
There	O
are	O
various	O
types	O
of	O
Punter	B-Protocol
such	O
as	O
PET	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
(	O
PTP	O
)	O
,	O
C1	B-Protocol
and	O
C2	B-Protocol
.	O
</s>
<s>
The	O
PET	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
(	O
PTP	O
)	O
,	O
also	O
known	O
as	O
Punter	B-Protocol
or	O
Old	B-Protocol
Punter	I-Protocol
,	O
was	O
developed	O
by	O
Steve	O
Punter	B-Protocol
for	O
use	O
with	O
his	O
PETBBS	O
and	O
BBS64	O
bulletin	B-Application
board	I-Application
system	I-Application
(	O
BBS	B-Application
)	O
software	O
.	O
</s>
<s>
The	O
"	O
PET	O
"	O
in	O
the	O
name	O
comes	O
from	O
the	O
Commodore	B-Device
PET	I-Device
computer	O
.	O
</s>
<s>
Compared	O
to	O
other	O
contemporary	O
protocols	O
,	O
PTP	O
is	O
slower	O
than	O
YMODEM	B-Protocol
and	O
ZMODEM	B-Device
but	O
faster	O
and	O
more	O
reliable	O
than	O
XMODEM	B-Protocol
.	O
</s>
<s>
The	O
earliest	O
version	O
of	O
Punter	B-Protocol
supports	O
only	O
7-bit	O
transfers	O
and	O
uses	O
a	O
back-correction	O
algorithm	O
involving	O
two	O
checksums	B-Algorithm
for	O
failsafes	O
.	O
</s>
<s>
One	O
of	O
the	O
two	O
checksums	B-Algorithm
is	O
additive	O
,	O
and	O
the	O
other	O
is	O
Boolean	O
in	O
nature	O
(	O
executing	O
EOR	O
instructions	O
)	O
,	O
making	O
for	O
an	O
easy	O
to	O
understand	O
algorithm	O
for	O
other	O
programmers	O
to	O
understand	O
and	O
emulate	O
.	O
</s>
<s>
Having	O
two	O
checksums	B-Algorithm
both	O
of	O
them	O
being	O
16	O
bits	O
wide	O
makes	O
it	O
significantly	O
more	O
accurate	O
than	O
the	O
single-byte	O
checksum	B-Algorithm
used	O
by	O
XMODEM	B-Protocol
,	O
its	O
major	O
competitor	O
in	O
the	O
early	O
1980s	O
.	O
</s>
<s>
Regardless	O
of	O
the	O
potential	O
for	O
errors	O
to	O
creep	O
in	O
,	O
in	O
comparison	O
to	O
the	O
YMODEM	B-Protocol
protocol	O
of	O
the	O
late	O
1980s	O
,	O
which	O
is	O
arguably	O
superior	O
,	O
it	O
has	O
been	O
widely	O
used	O
on	O
Commodore	B-Device
PET	I-Device
and	O
Commodore	O
64	O
based	O
bulletin	B-Application
boards	I-Application
.	O
</s>
<s>
Unlike	O
modern	O
computers	O
,	O
the	O
C64	O
and	O
C128	O
can	O
poll	O
the	O
User	O
Port	O
(	O
where	O
the	O
modem	B-Application
is	O
interfaced	O
)	O
at	O
slightly	O
different	O
baud	O
rates	O
and	O
connection	O
speeds	O
.	O
</s>
<s>
In	O
1984	O
,	O
Steve	O
Punter	B-Protocol
released	O
a	O
successor	O
to	O
PTP	O
called	O
C1	B-Protocol
,	O
or	O
New	B-Protocol
Punter	I-Protocol
.	O
</s>
<s>
C1	B-Protocol
was	O
the	O
standard	O
protocol	O
for	O
use	O
on	O
Commodore	O
BBSes	B-Application
,	O
and	O
was	O
rarely	O
supported	O
by	O
terminal	B-Application
or	O
BBS	B-Application
software	O
for	O
other	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
The	O
C1	B-Protocol
specification	O
was	O
rife	O
with	O
inaccuracies	O
and	O
ambiguities	O
,	O
making	O
it	O
difficult	O
to	O
implement	O
from	O
scratch	O
.	O
</s>
<s>
Nevertheless	O
,	O
the	O
protocol	O
came	O
into	O
widespread	O
use	O
because	O
Punter	B-Protocol
released	O
the	O
source	O
code	O
for	O
the	O
original	O
implementation	O
into	O
the	O
public	O
domain	O
.	O
</s>
<s>
C1	B-Protocol
could	O
transmit	O
block	O
sizes	O
up	O
to	O
255	O
bytes	B-Application
with	O
a	O
recommended	O
(	O
but	O
not	O
enforced	O
)	O
minimum	O
of	O
40	O
bytes	B-Application
and	O
an	O
overhead	O
of	O
7	O
bytes	B-Application
per	O
block	O
.	O
</s>
<s>
It	O
is	O
optimized	O
for	O
transferring	O
files	O
stored	O
by	O
8-bit	O
Commodore	O
computers	O
,	O
whose	O
DOS	B-Device
treats	O
executable	O
and	O
sequential	O
files	O
identically	O
.	O
</s>
<s>
The	O
term	O
Multi-Punter	B-Protocol
can	O
refer	O
to	O
any	O
one	O
of	O
three	O
or	O
four	O
mutually	O
incompatible	O
third-party	O
variants	O
of	O
C1	B-Protocol
which	O
permit	O
batch-file	O
transfers	O
,	O
as	O
opposed	O
to	O
C1	B-Protocol
,	O
which	O
was	O
designed	O
for	O
single-file	O
transfers	O
.	O
</s>
<s>
One	O
such	O
variant	O
,	O
C2	B-Protocol
,	O
also	O
known	O
simply	O
as	O
Punter	B-Protocol
,	O
was	O
developed	O
by	O
Punter	B-Protocol
.	O
</s>
<s>
As	O
with	O
C1	B-Protocol
,	O
it	O
is	O
optimized	O
for	O
transferring	O
files	O
stored	O
by	O
8-bit	O
Commodore	O
computers	O
.	O
</s>
