<s>
The	O
Burroughs	O
B1000	O
Series	O
was	O
a	O
series	O
of	O
mainframe	B-Architecture
computers	I-Architecture
,	O
built	O
by	O
the	O
Burroughs	O
Corporation	O
,	O
and	O
originally	O
introduced	O
in	O
the	O
1970s	O
with	O
continued	O
software	O
development	O
until	O
1987	O
.	O
</s>
<s>
The	O
series	O
consisted	O
of	O
three	O
major	O
generations	O
which	O
were	O
the	O
B1700	B-Device
,	O
B1800	O
,	O
and	O
B1900	O
series	O
machines	O
.	O
</s>
<s>
They	O
were	O
also	O
known	O
as	O
the	O
Burroughs	B-Device
Small	I-Device
Systems	I-Device
,	O
by	O
contrast	O
with	O
the	O
Burroughs	B-Device
Large	I-Device
Systems	I-Device
(	O
B5000	O
,	O
B6000	O
,	O
B7000	O
,	O
B8000	O
)	O
and	O
the	O
Burroughs	B-Language
Medium	I-Language
Systems	I-Language
(	O
B2000	B-Language
,	O
B3000	O
,	O
B4000	O
)	O
.	O
</s>
<s>
Much	O
of	O
the	O
original	O
research	O
for	O
the	O
B1700	B-Device
,	O
initially	O
codenamed	O
the	O
PLP	O
(	O
"	O
Proper	O
Language	O
Processor	O
"	O
or	O
"	O
Program	O
Language	O
Processor	O
"	O
)	O
,	O
was	O
done	O
at	O
the	O
Burroughs	O
Pasadena	O
plant	O
.	O
</s>
<s>
Production	O
of	O
the	O
B1700s	B-Device
began	O
in	O
the	O
mid-1970s	O
and	O
occurred	O
at	O
both	O
the	O
Santa	O
Barbara	O
and	O
Liège	O
,	O
Belgium	O
plants	O
.	O
</s>
<s>
The	O
B1000	O
is	O
distinguished	O
from	O
other	O
machines	O
in	O
that	O
it	O
had	O
a	O
writeable	B-General_Concept
control	I-General_Concept
store	I-General_Concept
allowing	O
the	O
machine	O
to	O
emulate	B-Application
any	O
other	O
machine	O
.	O
</s>
<s>
The	O
Burroughs	B-Application
MCP	I-Application
(	O
Master	B-Application
Control	I-Application
Program	I-Application
)	O
would	O
schedule	O
a	O
particular	O
job	B-General_Concept
to	O
run	O
.	O
</s>
<s>
The	O
MCP	B-Application
would	O
preload	O
the	O
interpreter	B-Application
for	O
whatever	O
language	O
was	O
required	O
.	O
</s>
<s>
These	O
interpreters	B-Application
presented	O
different	O
virtual	B-Architecture
machines	I-Architecture
for	O
COBOL	B-Application
,	O
Fortran	B-Application
,	O
etc	O
.	O
</s>
<s>
The	O
three	O
Burroughs	O
architectures	O
represent	O
solving	O
this	O
problem	O
by	O
building	O
hardware	O
aligned	O
with	O
high-level	O
languages	O
,	O
so-called	O
language-directed	B-Architecture
design	I-Architecture
(	O
contemporary	O
term	O
;	O
today	O
more	O
often	O
called	O
a	O
"	O
high-level	B-Architecture
language	I-Architecture
computer	I-Architecture
architecture	I-Architecture
"	O
)	O
.	O
</s>
<s>
The	O
large	B-Device
systems	I-Device
were	O
stack	B-Application
machines	I-Application
and	O
very	O
efficiently	O
executed	O
ALGOL	B-Language
.	O
</s>
<s>
The	O
medium	B-Language
systems	I-Language
(	O
B2000	B-Language
,	O
3000	O
,	O
and	O
B4000	O
)	O
were	O
aimed	O
at	O
the	O
business	O
world	O
and	O
executing	O
COBOL	B-Application
(	O
thus	O
everything	O
was	O
done	O
with	O
BCD	O
including	O
addressing	O
memory	O
.	O
)	O
</s>
<s>
The	O
B1000	O
series	O
was	O
perhaps	O
the	O
only	O
"	O
universal	O
"	O
solution	O
from	O
this	O
perspective	O
because	O
it	O
used	O
idealized	O
virtual	B-Architecture
machines	I-Architecture
for	O
any	O
language	O
.	O
</s>
<s>
Perhaps	O
the	O
most	O
obvious	O
examples	O
were	O
the	O
bit-addressable	O
memory	O
,	O
the	O
variable	O
size	O
arithmetic	B-General_Concept
logic	I-General_Concept
unit	I-General_Concept
(	O
ALU	B-General_Concept
)	O
,	O
and	O
the	O
ability	O
to	O
OR	O
in	O
data	O
from	O
a	O
register	O
into	O
the	O
instruction	O
register	O
allowing	O
very	O
efficient	O
instruction	O
parsing	O
.	O
</s>
<s>
Another	O
feature	O
of	O
the	O
machine	O
language	O
was	O
the	O
appearance	O
of	O
having	O
the	O
output	O
of	O
the	O
ALU	B-General_Concept
appear	O
as	O
different	O
addressable	O
registers	O
.	O
</s>
<s>
One	O
concession	O
to	O
the	O
fact	O
that	O
Burroughs	O
was	O
primarily	O
a	O
supplier	O
to	O
business	O
(	O
and	O
thus	O
running	O
COBOL	B-Application
)	O
was	O
the	O
availability	O
of	O
BCD	O
arithmetic	O
in	O
the	O
ALU	B-General_Concept
.	O
</s>
<s>
Internally	O
,	O
the	O
machines	O
employed	O
16-bit	B-Device
instructions	O
and	O
a	O
24-bit	O
data	O
path	O
.	O
</s>
<s>
The	O
initial	O
hardware	O
implementations	O
were	O
built	O
out	O
of	O
the	O
Complementary	O
Transistor	O
Logic	O
(	O
CTL	O
)	O
Family	O
originally	O
made	O
by	O
Fairchild	O
Semiconductor	O
but	O
with	O
the	O
introduction	O
of	O
the	O
B1955	O
in	O
1979	O
the	O
series	O
employed	O
the	O
more	O
popular	O
(	O
and	O
more	O
readily	O
obtainable	O
)	O
TTL	B-General_Concept
logic	I-General_Concept
family	O
.	O
</s>
<s>
Up	O
through	O
the	O
B1955	O
,	O
the	O
control	O
logic	O
was	O
implemented	O
with	O
PROMs	B-General_Concept
,	O
muxes	O
and	O
such	O
.	O
</s>
<s>
The	O
B1965	O
,	O
the	O
last	O
of	O
the	O
series	O
,	O
was	O
implemented	O
with	O
a	O
pair	O
of	O
microcode	B-Device
sequencers	O
which	O
stayed	O
in	O
lock	O
step	O
with	O
each	O
other	O
.	O
</s>
<s>
This	O
first	O
cycle	O
was	O
decoded	O
by	O
FPLAs	B-Architecture
using	O
16	O
inputs	O
(	O
just	O
the	O
perfect	O
size	O
for	O
a	O
16-bit	B-Device
instruction	O
word	O
)	O
and	O
48	O
min-terms	O
.	O
</s>
<s>
Successive	O
cycles	O
from	O
a	O
multi-cycle	O
instruction	O
were	O
sourced	O
from	O
PROMs	B-General_Concept
.	O
</s>
<s>
The	O
FPLAs	B-Architecture
and	O
PROM	O
outputs	O
were	O
wired	O
together	O
.	O
</s>
<s>
The	O
PROMs	B-General_Concept
would	O
drive	O
the	O
control	O
lines	O
until	O
the	O
completion	O
of	O
the	O
instruction	O
.	O
</s>
<s>
The	O
Multi-Line	O
was	O
capable	O
of	O
driving	O
multiple	O
19.2Kb	O
RS485	O
serial	O
lines	O
in	O
a	O
multi-drop	B-Architecture
configuration	O
.	O
</s>
<s>
The	O
Multi-Line	O
Adapter	O
would	O
DMA	B-General_Concept
the	O
data	O
into	O
main	O
memory	O
in	O
a	O
linked	B-Data_Structure
list	I-Data_Structure
format	O
.	O
</s>
