<s>
The	O
Macintosh	O
Communications	B-Operating_System
Toolbox	I-Operating_System
,	O
generally	O
shortened	O
to	O
CommToolbox	O
or	O
CTB	O
,	O
was	O
a	O
suite	O
of	O
application	B-Application
programming	I-Application
interfaces	I-Application
,	O
libraries	B-Library
and	O
dynamically	O
loaded	O
code	O
modules	O
for	O
the	O
classic	B-Application
Mac	I-Application
OS	I-Application
that	O
implemented	O
a	O
wide	O
variety	O
of	O
serial	B-Protocol
and	O
network	B-Architecture
communication	O
protocols	O
,	O
as	O
well	O
as	O
file	O
transfer	O
protocols	O
and	O
terminal	B-Application
emulations	I-Application
.	O
</s>
<s>
Using	O
CommToolbox	O
,	O
one	O
could	O
write	O
an	O
application	B-Application
that	O
would	O
seamlessly	O
work	O
over	O
AppleTalk	B-Application
,	O
a	O
modem	B-Application
or	O
any	O
variety	O
of	O
other	O
connections	O
,	O
transfer	O
files	O
using	O
XMODEM	B-Protocol
,	O
Kermit	B-Protocol
or	O
other	O
file	O
transfer	O
protocols	O
,	O
and	O
provide	O
DEC	B-Device
VT102	I-Device
,	O
VT220	B-Device
,	O
IBM	B-Operating_System
3270	I-Operating_System
and	O
other	O
terminal	B-Application
emulation	I-Application
services	O
.	O
</s>
<s>
Developers	O
could	O
also	O
write	O
plug-in	O
communications	O
modules	O
known	O
as	O
"	O
Tools	O
"	O
,	O
allowing	O
any	O
CommToolbox-aware	O
application	B-Application
to	O
use	O
that	O
connection	O
method	O
.	O
</s>
<s>
Examples	O
of	O
applications	O
using	O
it	O
for	O
simple	O
tasks	O
were	O
common	O
,	O
but	O
single-purpose	O
applications	O
would	O
have	O
higher	O
performance	O
when	O
bypassing	O
system	O
API	B-Application
's	O
implementations	O
and	O
rolling	O
their	O
own	O
.	O
</s>
<s>
CommToolbox	O
was	O
initially	O
released	O
independent	O
of	O
the	O
main	O
Mac	O
system	O
releases	O
but	O
was	O
finally	O
integrated	O
and	O
delivered	O
with	O
System	B-Operating_System
7	I-Operating_System
.	O
</s>
<s>
The	O
development	O
team	O
was	O
part	O
of	O
the	O
Apple	O
Networking	O
and	O
Communications	O
Division	O
,	O
not	O
part	O
of	O
the	O
main	O
System	B-Application
Software	I-Application
team	O
.	O
</s>
<s>
CommToolbox	O
was	O
perhaps	O
one	O
of	O
the	O
first	O
implementations	O
of	O
shared	O
libraries	B-Library
on	O
the	O
early	O
Mac	B-Application
OS	I-Application
.	O
</s>
<s>
CommToolbox	O
API	B-Application
's	O
consisted	O
of	O
4	O
managers	O
:	O
</s>
<s>
The	O
CRM	O
provided	O
the	O
Mac	O
with	O
its	O
first	O
centralized	O
repository	O
to	O
register	O
and	O
enumerate	O
serial	B-Protocol
devices	O
.	O
</s>
<s>
Early	O
Mac	O
's	O
only	O
had	O
two	O
serial	B-Protocol
ports	O
and	O
with	O
the	O
later	O
Mac	O
's	O
allowing	O
expandability	O
including	O
serial	B-Protocol
port	O
cards	O
,	O
the	O
CRM	O
filled	O
a	O
critical	O
hole	O
in	O
the	O
Mac	B-Application
OS	I-Application
software	O
architecture	O
.	O
</s>
<s>
Device	O
manufacturers	O
would	O
create	O
a	O
pair	O
of	O
drivers	O
that	O
provided	O
the	O
same	O
interface	O
as	O
Apple	O
's	O
built-in	O
serial	B-Protocol
port	O
drivers	O
(	O
but	O
named	O
differently	O
from	O
.AIn/.AOut	O
.BIn/.BOut	O
)	O
and	O
register	O
these	O
drivers	O
with	O
the	O
CRM	O
.	O
</s>
<s>
The	O
Connection	O
,	O
File	O
Transfer	O
and	O
Terminal	O
Manager	O
's	O
all	O
worked	O
with	O
their	O
respective	O
tools	O
which	O
were	O
dynamically	O
loaded	O
code	O
modules	O
providing	O
the	O
interface	O
between	O
the	O
Manager-specific	O
API	B-Application
and	O
the	O
code	O
implementing	O
the	O
particular	O
functionality	O
.	O
</s>
<s>
In	O
this	O
manner	O
,	O
an	O
application	B-Application
could	O
be	O
written	O
"	O
agnostically	O
"	O
without	O
implementation-specific	O
knowledge	O
of	O
any	O
particular	O
data	O
connection	O
,	O
file	O
transfer	O
,	O
or	O
terminal	B-Application
emulation	I-Application
protocols	O
.	O
</s>
<s>
Terminal	O
Tools	O
implemented	O
the	O
character	O
conversion	O
and	O
command	O
string	O
interpretation	O
needed	O
to	O
support	O
any	O
sort	O
of	O
terminal	B-Application
emulator	I-Application
(	O
mainly	O
text	O
terminals	O
,	O
graphics	O
terminal	O
tools	O
were	O
never	O
released	O
)	O
,	O
and	O
would	O
be	O
responsible	O
for	O
handling	O
rendering	O
into	O
a	O
QuickDraw	B-Operating_System
GrafPort	I-Operating_System
,	O
user	O
interactions	O
including	O
copying	O
text	O
out	O
of	O
the	O
terminal	O
buffer	O
,	O
and	O
managing	O
keystrokes	O
to	O
send	O
terminal-specific	O
control	O
strings	O
.	O
</s>
<s>
A	O
typical	O
terminal	B-Application
emulator	I-Application
application	B-Application
would	O
use	O
all	O
of	O
them	O
,	O
connecting	O
a	O
Connection	O
Tool	O
selected	O
in	O
the	O
Connection	O
Manager	O
to	O
Terminal	O
Tool	O
in	O
the	O
Terminal	O
Manager	O
,	O
and	O
then	O
periodically	O
using	O
a	O
File	O
Transfer	O
Tool	O
in	O
the	O
File	O
Transfer	O
Manager	O
on	O
user	O
request	O
.	O
</s>
<s>
Such	O
was	O
the	O
case	O
for	O
common	O
terminal	B-Application
emulators	I-Application
like	O
VersaTerm	O
and	O
MacTerminal	B-Operating_System
.	O
</s>
<s>
However	O
,	O
another	O
application	B-Application
might	O
use	O
only	O
one	O
of	O
these	O
,	O
say	O
the	O
Connection	O
Manager	O
to	O
set	O
up	O
communications	O
.	O
</s>
<s>
QuickMail	O
and	O
Eudora	B-Application
are	O
well-known	O
examples	O
.	O
</s>
<s>
Perhaps	O
the	O
best	O
known	O
Tool	O
was	O
the	O
Apple	O
Modem	B-Application
Tool	O
,	O
which	O
provided	O
the	O
serial	B-Protocol
communications	I-Protocol
drivers	O
as	O
well	O
as	O
a	O
system	O
for	O
storing	O
setup	B-Device
commands	I-Device
.	O
</s>
<s>
This	O
was	O
during	O
an	O
era	O
where	O
there	O
was	O
a	O
proliferation	O
of	O
different	O
modem	B-Application
vendors	O
,	O
each	O
with	O
subtly	O
and	O
not-so-subtly	O
different	O
AT	B-Device
command	I-Device
strings	O
needed	O
for	O
configuration	O
.	O
</s>
<s>
When	O
a	O
connection	O
was	O
initiated	O
using	O
the	O
Modem	B-Application
Tool	O
,	O
the	O
link	O
to	O
the	O
modem	B-Application
was	O
opened	O
,	O
commands	O
sent	O
to	O
it	O
,	O
and	O
the	O
link	O
established	O
by	O
dialling	O
.	O
</s>
<s>
The	O
Apple	O
Modem	B-Application
Tool	O
faced	O
challenges	O
with	O
keeping	O
with	O
the	O
rapidly	O
changing	O
modem	B-Application
landscape	O
with	O
needing	O
to	O
track	O
higher	O
speeds	O
and	O
new	O
features	O
being	O
regularly	O
introduced	O
by	O
modem	B-Application
vendors	O
.	O
</s>
<s>
Providing	O
CTB	O
updates	O
in	O
general	O
was	O
also	O
a	O
challenge	O
as	O
the	O
CTB	O
development	O
was	O
,	O
at	O
first	O
,	O
not	O
part	O
of	O
the	O
main	O
System	B-Application
Software	I-Application
effort	O
,	O
but	O
rather	O
part	O
of	O
the	O
Networking	O
and	O
Communications	O
division	O
.	O
</s>
<s>
A	O
further	O
update	O
was	O
needed	O
to	O
support	O
higher	O
speeds	O
when	O
28kbit/s	O
modems	B-Application
become	O
common	O
.	O
</s>
<s>
Some	O
of	O
the	O
other	O
Apple	O
provided	O
tools	O
included	O
the	O
simple	O
Serial	B-Protocol
Tool	O
and	O
AppleTalk	B-Application
Tools	O
using	O
AppleTalk	B-Application
's	O
Apple	O
Data	O
Stream	O
Protocol	O
as	O
additional	O
connection	O
methods	O
,	O
the	O
TTY	O
and	O
VT102	B-Device
Tools	O
for	O
terminal	B-Application
emulation	I-Application
,	O
and	O
the	O
Text	O
and	O
XModem	B-Protocol
tools	O
for	O
file	O
transfers	O
.	O
</s>
<s>
Third	O
party	O
tools	O
were	O
common	O
for	O
supporting	O
connections	O
,	O
including	O
the	O
Global	B-Device
Village	I-Device
TelePort	I-Device
modem	B-Application
which	O
plugged	O
into	O
the	O
Apple	B-Device
Desktop	I-Device
Bus	I-Device
and	O
thus	O
required	O
custom	O
drivers	O
,	O
Apple	O
's	O
own	O
X.25	B-Protocol
and	O
ISDN	B-Protocol
tools	O
,	O
and	O
a	O
variety	O
of	O
other	O
examples	O
.	O
</s>
<s>
There	O
were	O
also	O
third-party	O
Telnet	B-Protocol
Connection	O
Tools	O
released	O
when	O
TCP/IP	O
started	O
becoming	O
prevalent	O
.	O
</s>
<s>
The	O
equipment	O
set-up	O
was	O
a	O
backlit	O
Mac	O
Portable	O
using	O
a	O
PSI	O
Integration	O
internal	O
fax	O
modem	B-Application
(	O
used	O
in	O
half	O
duplex	O
mode	O
due	O
to	O
the	O
nature	O
of	O
the	O
shuttle	O
air-to-ground	O
voice	O
links	O
)	O
.	O
</s>
<s>
The	O
communications	O
software	O
used	O
was	O
a	O
specially	O
modified	O
version	O
of	O
AppleLink	O
that	O
used	O
the	O
CommToolbox	O
Connection	O
Manager	O
(	O
instead	O
of	O
directly	O
accessing	O
serial	B-Protocol
ports	O
)	O
and	O
a	O
custom	O
Connection	O
Tool	O
written	O
pro	O
bono	O
by	O
three	O
Apple	O
engineers	O
in	O
their	O
spare	O
time	O
to	O
hide	O
the	O
half-duplex	O
nature	O
of	O
the	O
air-to-ground	O
link	O
from	O
the	O
application	B-Application
(	O
which	O
was	O
expecting	O
a	O
full-duplex	O
connection	O
)	O
.	O
</s>
