<s>
The	O
Burroughs	B-Device
Large	I-Device
Systems	I-Device
Group	O
produced	O
a	O
family	O
of	O
large	O
48-bit	O
mainframes	B-Architecture
using	O
stack	B-Application
machine	I-Application
instruction	B-General_Concept
sets	I-General_Concept
with	O
dense	O
syllables	B-General_Concept
.	O
</s>
<s>
It	O
was	O
optimized	O
for	O
compiling	O
ALGOL	B-Language
60	I-Language
programs	O
extremely	O
well	O
,	O
using	O
single-pass	B-Language
compilers	I-Language
.	O
</s>
<s>
Each	O
division	O
's	O
product	O
line	O
grew	O
from	O
a	O
different	O
concept	O
for	O
how	O
to	O
optimize	O
a	O
computer	O
's	O
instruction	B-General_Concept
set	I-General_Concept
for	O
particular	O
programming	O
languages	O
.	O
</s>
<s>
"	O
Burroughs	B-Device
Large	I-Device
Systems	I-Device
"	O
referred	O
to	O
all	O
of	O
these	O
large-system	O
product	O
lines	O
together	O
,	O
in	O
contrast	O
to	O
the	O
COBOL-optimized	O
Medium	B-Language
Systems	I-Language
(	O
B2000	B-Language
,	O
B3000	O
,	O
and	O
B4000	O
)	O
or	O
the	O
flexible-architecture	O
Small	B-Device
Systems	I-Device
(	O
B1000	O
)	O
.	O
</s>
<s>
By	O
the	O
late	O
1950s	O
its	O
computing	O
equipment	O
was	O
still	O
limited	O
to	O
electromechanical	O
accounting	B-Device
machines	I-Device
such	O
as	O
the	O
Sensimatic	O
.	O
</s>
<s>
Computers	O
using	O
that	O
architecture	O
were	O
still	O
in	O
production	O
as	O
the	O
Unisys	O
ClearPath	O
Libra	O
servers	O
which	O
run	O
an	O
evolved	O
but	O
compatible	O
version	O
of	O
the	O
MCP	B-Application
operating	B-General_Concept
system	I-General_Concept
first	O
introduced	O
with	O
the	O
B6700	O
.	O
</s>
<s>
In	O
addition	O
to	O
a	O
proprietary	O
CMOS	B-Device
processor	O
design	O
,	O
Unisys	O
also	O
uses	O
Intel	B-Device
Xeon	I-Device
processors	O
and	O
runs	O
MCP	B-Application
,	O
Microsoft	B-Application
Windows	I-Application
and	O
Linux	B-Application
operating	I-Application
systems	I-Application
on	O
their	O
Libra	O
servers	O
;	O
the	O
use	O
of	O
custom	O
chips	O
was	O
gradually	O
eliminated	O
,	O
and	O
by	O
2018	O
the	O
Libra	O
servers	O
had	O
been	O
strictly	O
commodity	O
Intel	O
for	O
some	O
years	O
.	O
</s>
<s>
While	O
there	O
was	O
no	O
successor	O
to	O
the	O
B5700	O
,	O
the	O
B5000	O
line	O
heavily	O
influenced	O
the	O
design	O
of	O
the	O
B6500	O
,	O
and	O
Burroughs	O
ported	O
the	O
Master	B-Application
Control	I-Application
Program	I-Application
(	O
MCP	B-Application
)	O
to	O
that	O
machine	O
.	O
</s>
<s>
No	O
Assembly	B-Language
language	I-Language
or	O
assembler	B-Language
;	O
all	O
system	O
software	O
written	O
in	O
an	O
extended	O
variety	O
of	O
ALGOL	B-Language
60	I-Language
named	O
ESPOL	B-Language
.	O
</s>
<s>
However	O
,	O
ESPOL	B-Language
had	O
statements	O
for	O
each	O
of	O
the	O
syllables	B-General_Concept
in	O
the	O
architecture	O
.	O
</s>
<s>
Stack	B-Application
machine	I-Application
where	O
all	O
operations	O
use	O
the	O
stack	O
rather	O
than	O
explicit	O
operands	O
.	O
</s>
<s>
All	O
code	O
automatically	O
reentrant	B-Operating_System
:	O
programmers	O
do	O
n't	O
have	O
to	O
do	O
anything	O
more	O
to	O
have	O
any	O
code	O
in	O
any	O
language	O
spread	O
across	O
processors	O
than	O
to	O
use	O
just	O
the	O
two	O
shown	O
simple	O
primitives	O
.	O
</s>
<s>
A	O
commercial	O
implementation	O
virtual	B-Architecture
memory	I-Architecture
,	O
preceded	O
only	O
by	O
the	O
Ferranti	B-Device
Atlas	I-Device
.	O
</s>
<s>
The	O
B5000	O
was	O
unusual	O
at	O
the	O
time	O
in	O
that	O
the	O
architecture	O
and	O
instruction	B-General_Concept
set	I-General_Concept
were	O
designed	O
with	O
the	O
needs	O
of	O
software	O
taken	O
into	O
consideration	O
.	O
</s>
<s>
This	O
was	O
a	O
large	O
departure	O
from	O
the	O
computer	O
system	O
design	O
of	O
the	O
time	O
,	O
where	O
a	O
processor	O
and	O
its	O
instruction	B-General_Concept
set	I-General_Concept
would	O
be	O
designed	O
and	O
then	O
handed	O
over	O
to	O
the	O
software	O
people	O
.	O
</s>
<s>
For	O
a	O
main	O
program	O
,	O
the	O
T	O
field	O
of	O
an	O
Operand	O
Call	O
or	O
Descriptor	B-Device
Call	O
syllable	B-General_Concept
is	O
relative	O
to	O
the	O
Program	O
Reference	O
Table	O
(	O
PRT	O
)	O
.	O
</s>
<s>
+B5x00	O
Relative	O
AddressingTaken	O
from	O
SALF	O
T0A38	O
T1A39	O
T2A40	O
MSFF	O
Base	O
Contents	O
Index	O
Sign	O
IndexBits	O
MaxIndex	O
OFF	O
-	O
-	O
-	O
-	O
R	O
Address	O
of	O
PRT	O
+	O
T	O
0-9A	O
38-47	O
1023	O
ON	O
OFF	O
-	O
-	O
-	O
R	O
Address	O
of	O
PRT	O
+	O
T	O
1-9A	O
39-47	O
511	O
ON	O
ON	O
OFF	O
-	O
OFF	O
F	O
Address	O
of	O
last	O
RCW	O
or	O
MSCW	O
on	O
stack	O
+	O
T	O
2-9A	O
40-47	O
255	O
ON	O
ON	O
OFF	O
-	O
ON	O
(	O
R+7	O
)	O
F	O
register	O
from	O
MSCW	O
at	O
PRT+7	O
+	O
T	O
2-9A	O
40-47	O
255	O
ON	O
ON	O
ON	O
OFF	O
-	O
C	B-Language
Address	O
of	O
current	O
instruction	O
word	O
+	O
T	O
3-9A	O
41-47	O
127	O
ON	O
ON	O
ON	O
ON	O
OFF	O
F	O
Address	O
of	O
last	O
RCW	O
or	O
MSCW	O
on	O
stack	O
-	O
T	O
3-9A	O
41-47	O
127	O
ON	O
ON	O
ON	O
ON	O
ON	O
(	O
R+7	O
)	O
F	O
register	O
from	O
MSCW	O
at	O
PRT+7	O
-	O
T	O
3-9A	O
41-47	O
127	O
Notes	O
:	O
</s>
<s>
The	O
B5000	O
was	O
designed	O
to	O
exclusively	O
support	O
high-level	B-Language
languages	I-Language
.	O
</s>
<s>
This	O
was	O
at	O
a	O
time	O
when	O
such	O
languages	O
were	O
just	O
coming	O
to	O
prominence	O
with	O
FORTRAN	B-Application
and	O
then	O
COBOL	B-Application
.	O
</s>
<s>
FORTRAN	B-Application
and	O
COBOL	B-Application
were	O
considered	O
weaker	O
languages	O
by	O
some	O
,	O
when	O
it	O
comes	O
to	O
modern	O
software	O
techniques	O
,	O
so	O
a	O
newer	O
,	O
mostly	O
untried	O
language	O
was	O
adopted	O
,	O
ALGOL-60	B-Language
.	O
</s>
<s>
The	O
ALGOL	B-Language
dialect	O
chosen	O
for	O
the	O
B5000	O
was	O
Elliott	B-Language
ALGOL	I-Language
,	O
first	O
designed	O
and	O
implemented	O
by	O
C	B-Language
.	O
A	O
.	O
R	O
.	O
Hoare	O
on	O
an	O
Elliott	B-Device
503	I-Device
.	O
</s>
<s>
This	O
was	O
a	O
practical	O
extension	O
of	O
ALGOL	B-Language
with	O
I/O	O
instructions	O
(	O
which	O
ALGOL	B-Language
had	O
ignored	O
)	O
and	O
powerful	O
string	O
processing	O
instructions	O
.	O
</s>
<s>
Donald	O
Knuth	O
had	O
previously	O
implemented	O
ALGOL	B-Language
58	I-Language
on	O
an	O
earlier	O
Burroughs	O
machine	O
during	O
the	O
three	O
months	O
of	O
his	O
summer	O
break	O
,	O
and	O
he	O
was	O
peripherally	O
involved	O
in	O
the	O
B5000	O
design	O
as	O
a	O
consultant	O
.	O
</s>
<s>
Many	O
wrote	O
ALGOL	B-Language
off	O
,	O
mistakenly	O
believing	O
that	O
high-level	B-Language
languages	I-Language
could	O
not	O
have	O
the	O
same	O
power	O
as	O
assembler	B-Language
,	O
and	O
thus	O
not	O
realizing	O
ALGOL	B-Language
's	O
potential	O
as	O
a	O
systems	O
programming	O
language	O
.	O
</s>
<s>
The	O
Burroughs	O
ALGOL	B-Language
compiler	O
was	O
very	O
fast	O
this	O
impressed	O
the	O
Dutch	O
scientist	O
Edsger	O
Dijkstra	O
when	O
he	O
submitted	O
a	O
program	O
to	O
be	O
compiled	O
at	O
the	O
B5000	O
Pasadena	O
plant	O
.	O
</s>
<s>
The	O
compiler	O
was	O
fast	O
for	O
several	O
reasons	O
,	O
but	O
the	O
primary	O
reason	O
was	O
that	O
it	O
was	O
a	O
one-pass	B-Language
compiler	I-Language
.	O
</s>
<s>
Early	O
computers	O
did	O
not	O
have	O
enough	O
memory	O
to	O
store	O
the	O
source	O
code	O
,	O
so	O
compilers	O
(	O
and	O
even	O
assemblers	B-Language
)	O
usually	O
needed	O
to	O
read	O
the	O
source	O
code	O
more	O
than	O
once	O
.	O
</s>
<s>
The	O
Burroughs	O
ALGOL	B-Language
syntax	O
,	O
unlike	O
the	O
official	O
language	O
,	O
requires	O
that	O
each	O
variable	O
(	O
or	O
other	O
object	O
)	O
be	O
declared	O
before	O
it	O
is	O
used	O
,	O
so	O
it	O
is	O
feasible	O
to	O
write	O
an	O
ALGOL	B-Language
compiler	O
that	O
reads	O
the	O
data	O
only	O
once	O
.	O
</s>
<s>
Burroughs	B-Device
large	I-Device
systems	I-Device
could	O
compile	O
as	O
fast	O
as	O
they	O
could	O
read	O
the	O
source	O
code	O
from	O
the	O
punched	B-Architecture
cards	I-Architecture
,	O
and	O
they	O
had	O
the	O
fastest	O
card	O
readers	O
in	O
the	O
industry	O
.	O
</s>
<s>
The	O
powerful	O
Burroughs	O
COBOL	B-Application
compiler	O
was	O
also	O
a	O
one-pass	B-Language
compiler	I-Language
and	O
equally	O
fast	O
.	O
</s>
<s>
A	O
4000-card	O
COBOL	B-Application
program	O
compiled	O
as	O
fast	O
as	O
the	O
1000-card/minute	O
readers	O
could	O
read	O
the	O
code	O
.	O
</s>
<s>
The	O
B6500	O
had	O
variable	O
length	O
instructions	O
with	O
an	O
8-bit	O
syllable	B-General_Concept
instead	O
of	O
fixed	O
length	O
instructions	O
with	O
a	O
12-bit	O
syllable	B-General_Concept
.	O
</s>
<s>
The	O
B6500	O
used	O
monolithic	O
integrated	O
circuits	O
with	O
magnetic	O
thin-film	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
The	O
system	O
used	O
monolithic	O
integrated	O
circuits	O
with	O
magnetic	O
thin-film	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
The	O
central	O
concept	O
of	O
virtual	B-Architecture
memory	I-Architecture
appeared	O
in	O
the	O
designs	O
of	O
the	O
Ferranti	B-Device
Atlas	I-Device
and	O
the	O
Rice	B-Device
Institute	I-Device
Computer	I-Device
,	O
and	O
the	O
central	O
concepts	O
of	O
descriptors	O
and	O
tagged	B-Architecture
architecture	I-Architecture
appeared	O
in	O
the	O
design	O
of	O
the	O
Rice	B-Device
Institute	I-Device
Computer	I-Device
in	O
the	O
late	O
1950s	O
.	O
</s>
<s>
However	O
,	O
even	O
if	O
those	O
designs	O
had	O
a	O
direct	O
influence	O
on	O
Burroughs	O
,	O
the	O
architectures	O
of	O
the	O
B5000	O
,	O
B6500	O
and	O
B8500	O
were	O
very	O
different	O
from	O
those	O
of	O
the	O
Atlas	B-Device
and	O
the	O
Rice	O
machine	O
;	O
they	O
are	O
also	O
very	O
different	O
from	O
each	O
other	O
.	O
</s>
<s>
The	O
first	O
of	O
the	O
Burroughs	B-Device
large	I-Device
systems	I-Device
was	O
the	O
B5000	O
.	O
</s>
<s>
Designed	O
in	O
1961	O
,	O
it	O
was	O
a	O
second-generation	B-Device
computer	I-Device
using	O
discrete	O
transistor	O
logic	O
and	O
magnetic-core	O
memory	O
,	O
followed	O
by	O
the	O
B5500	O
and	O
B5700	O
.	O
</s>
<s>
After	O
a	O
merger	O
in	O
which	O
Burroughs	O
acquired	O
Sperry	O
Corporation	O
and	O
changed	O
its	O
name	O
to	O
Unisys	O
,	O
the	O
company	O
continued	O
to	O
develop	O
new	O
machines	O
based	O
on	O
the	O
MCP	B-Application
CMOS	B-Device
ASIC	O
.	O
</s>
<s>
Later	O
Libras	O
,	O
including	O
the	O
590	O
,	O
also	O
incorporate	O
Intel	B-Device
Xeon	I-Device
processors	O
and	O
can	O
run	O
the	O
Burroughs	B-Device
large	I-Device
systems	I-Device
architecture	O
in	O
emulation	O
as	O
well	O
as	O
on	O
the	O
MCP	B-Application
CMOS	B-Device
processors	O
.	O
</s>
<s>
It	O
is	O
unclear	O
if	O
Unisys	O
will	O
continue	O
development	O
of	O
new	O
MCP	B-Application
CMOS	B-Device
ASICs	O
.	O
</s>
<s>
semiconductor	O
memory	O
,	O
NUMA	B-Operating_System
architecture	O
B7800	O
1977	O
?	O
</s>
<s>
semiconductor	O
memory	O
,	O
NUMA	B-Operating_System
architecture	O
.	O
</s>
<s>
Max	O
of	O
4	O
B6900	O
CPUs	O
bound	O
to	O
a	O
local	O
memory	O
and	O
a	O
common	O
Global	O
Memory(tm )	O
B5900	O
1981	O
semiconductor	O
memory	O
,	O
NUMA	B-Operating_System
architecture	O
.	O
</s>
<s>
semiconductor	O
memory	O
,	O
faster	O
,	O
code	O
&	O
data	O
caches	O
,	O
NUMA	B-Operating_System
architecture	O
,	O
</s>
<s>
1-2	O
HDUs	O
(	O
I/O	O
)	O
,	O
1-2	O
APs	O
,	O
1-4	O
CPUs	O
,	O
Soft	O
implementation	O
of	O
NUMA	B-Operating_System
memory	O
allowed	O
CPUs	O
to	O
float	O
from	O
memory	O
space	O
to	O
memory	O
space	O
.	O
</s>
<s>
A9/A10	O
1984	O
B6000	O
class	O
,	O
First	O
pipelined	O
processor	O
in	O
the	O
mid-range	O
,	O
single	O
CPU	O
(	O
dual	O
on	O
A10	O
)	O
,	O
First	O
to	O
support	O
eMode	O
Beta	O
(	O
expanded	O
Memory	O
Addressing	O
)	O
A12/A15	O
1985	O
B7000	O
class	O
,	O
Re-implemented	O
in	O
custom-designed	O
Motorola	O
ECL	B-General_Concept
MCA1	O
,	O
then	O
MCA2	O
gate	O
arrays	O
,	O
single	O
CPU	O
single	O
HDU	O
(	O
A12	O
)	O
1	O
–	O
4	O
CPU	O
,	O
1	O
–	O
2	O
HDU	O
(	O
A15	O
)	O
Micro	O
A	O
1989	O
desktop	O
"	O
mainframe	B-Architecture
"	O
with	O
single-chip	O
SCAMP	O
processor	O
.	O
</s>
<s>
Clearpath	O
HMP	O
LX	O
5000	O
1998	O
Implements	O
Burroughs	B-Device
Large	I-Device
systems	I-Device
in	O
emulation	O
only	O
(	O
Xeon	B-Device
processors	O
)	O
Libra	O
100	O
2002	O
?	O
</s>
<s>
Newer	O
and	O
larger	O
models	O
had	O
instructions	O
which	O
were	O
not	O
supported	O
on	O
older	O
and	O
slower	O
models	O
,	O
but	O
the	O
hardware	O
,	O
when	O
encountering	O
an	O
unrecognized	O
instruction	O
,	O
invoked	O
an	O
operating	B-General_Concept
system	I-General_Concept
function	O
which	O
interpreted	O
it	O
.	O
</s>
<s>
The	O
Burroughs	B-Device
large	I-Device
systems	I-Device
implement	O
an	O
ALGOL-derived	O
stack	B-Application
architecture	I-Application
.	O
</s>
<s>
While	O
B5000	O
was	O
specifically	O
designed	O
to	O
support	O
ALGOL	B-Language
,	O
this	O
was	O
only	O
a	O
starting	O
point	O
.	O
</s>
<s>
Other	O
business-oriented	O
languages	O
such	O
as	O
COBOL	B-Application
were	O
also	O
well	O
supported	O
,	O
most	O
notably	O
by	O
the	O
powerful	O
string	O
operators	O
which	O
were	O
included	O
for	O
the	O
development	O
of	O
fast	O
compilers	O
.	O
</s>
<s>
The	O
ALGOL	B-Language
used	O
on	O
the	O
B5000	O
is	O
an	O
extended	O
ALGOL	B-Language
subset	O
.	O
</s>
<s>
It	O
includes	O
powerful	O
string	O
manipulation	O
instructions	O
but	O
excludes	O
certain	O
ALGOL	B-Language
constructs	O
,	O
notably	O
unspecified	O
formal	O
parameters	O
.	O
</s>
<s>
A	O
DEFINE	O
mechanism	O
serves	O
a	O
similar	O
purpose	O
to	O
the	O
#defines	B-Language
found	O
in	O
C	B-Language
,	O
but	O
is	O
fully	O
integrated	O
into	O
the	O
language	O
rather	O
than	O
being	O
a	O
preprocessor	O
.	O
</s>
<s>
The	O
user	O
level	O
of	O
ALGOL	B-Language
does	O
not	O
include	O
many	O
of	O
the	O
insecure	O
constructs	O
needed	O
by	O
the	O
operating	B-General_Concept
system	I-General_Concept
and	O
other	O
system	O
software	O
.	O
</s>
<s>
Two	O
levels	O
of	O
language	O
extensions	O
provide	O
the	O
additional	O
constructs	O
:	O
ESPOL	B-Language
and	O
NEWP	B-Language
for	O
writing	O
the	O
MCP	B-Application
and	O
closely	O
related	O
software	O
,	O
and	O
DCALGOL	O
and	O
DMALGOL	O
to	O
provide	O
more	O
specific	O
extensions	O
for	O
specific	O
kinds	O
of	O
system	O
software	O
.	O
</s>
<s>
Originally	O
,	O
the	O
B5000	O
MCP	B-Application
operating	B-General_Concept
system	I-General_Concept
was	O
written	O
in	O
an	O
extension	O
of	O
extended	O
ALGOL	B-Language
called	O
ESPOL	B-Language
(	O
Executive	O
Systems	O
Programming	O
Oriented	O
Language	O
)	O
.	O
</s>
<s>
This	O
was	O
replaced	O
in	O
the	O
mid-to-late	O
70s	O
by	O
a	O
language	O
called	O
NEWP	B-Language
.	O
</s>
<s>
Though	O
NEWP	B-Language
probably	O
just	O
meant	O
"	O
New	O
Programming	O
language	O
"	O
,	O
legends	O
surround	O
the	O
name	O
.	O
</s>
<s>
Another	O
story	O
is	O
that	O
circa	O
1976	O
,	O
John	O
McClintock	O
of	O
Burroughs	O
(	O
the	O
software	O
engineer	O
developing	O
NEWP	B-Language
)	O
named	O
the	O
language	O
"	O
NEWP	B-Language
"	O
after	O
being	O
asked	O
,	O
yet	O
again	O
,	O
"	O
does	O
it	O
have	O
a	O
name	O
yet	O
"	O
:	O
answering	O
"	O
nyoooop	O
"	O
,	O
he	O
adopted	O
that	O
as	O
a	O
name	O
.	O
</s>
<s>
NEWP	B-Language
,	O
too	O
,	O
was	O
a	O
subset	O
ALGOL	B-Language
extension	O
,	O
but	O
it	O
was	O
more	O
secure	O
than	O
ESPOL	B-Language
,	O
and	O
dropped	O
some	O
little-used	O
complexities	O
of	O
ALGOL	B-Language
.	O
</s>
<s>
In	O
fact	O
,	O
all	O
unsafe	O
constructs	O
are	O
rejected	O
by	O
the	O
NEWP	B-Language
compiler	O
unless	O
a	O
block	O
is	O
specifically	O
marked	O
to	O
allow	O
those	O
instructions	O
.	O
</s>
<s>
NEWP	B-Language
programs	O
that	O
contain	O
unsafe	O
constructs	O
are	O
initially	O
non-executable	O
.	O
</s>
<s>
While	O
NEWP	B-Language
can	O
be	O
used	O
to	O
write	O
general	O
programs	O
and	O
has	O
a	O
number	O
of	O
features	O
designed	O
for	O
large	O
software	O
projects	O
,	O
it	O
does	O
not	O
support	O
everything	O
ALGOL	B-Language
does	O
.	O
</s>
<s>
NEWP	B-Language
has	O
a	O
number	O
of	O
facilities	O
to	O
enable	O
large-scale	O
software	O
projects	O
,	O
such	O
as	O
the	O
operating	B-General_Concept
system	I-General_Concept
,	O
including	O
named	O
interfaces	O
(	O
functions	O
and	O
data	O
)	O
,	O
groups	O
of	O
interfaces	O
,	O
modules	O
,	O
and	O
super-modules	O
.	O
</s>
<s>
The	O
second	O
intermediate	O
level	O
of	O
security	O
between	O
operating	B-General_Concept
system	I-General_Concept
code	O
(	O
in	O
NEWP	B-Language
)	O
and	O
user	O
programs	O
(	O
in	O
ALGOL	B-Language
)	O
is	O
for	O
middleware	B-General_Concept
programs	O
,	O
which	O
are	O
written	O
in	O
DCALGOL	O
(	O
data	O
comms	O
ALGOL	B-Language
)	O
.	O
</s>
<s>
Middleware	B-General_Concept
such	O
as	O
COMS	O
(	O
introduced	O
around	O
1984	O
)	O
receive	O
messages	O
from	O
around	O
the	O
network	O
and	O
dispatch	O
these	O
messages	O
to	O
specific	O
handling	O
processes	O
or	O
to	O
an	O
MCS	O
(	O
Message	O
Control	O
System	O
)	O
such	O
as	O
CANDE	B-Operating_System
(	O
"	O
Command	O
AND	O
Edit	O
,	O
"	O
the	O
program	O
development	O
environment	O
)	O
.	O
</s>
<s>
In	O
the	O
early	O
years	O
the	O
DCP	O
did	O
have	O
an	O
assembler	B-Language
(	O
Dacoma	O
)	O
,	O
an	O
application	O
program	O
called	O
DCPProgen	O
written	O
in	O
B6500	O
ALGOL	B-Language
.	O
</s>
<s>
Later	O
the	O
NDL	B-Device
(	O
Network	B-Device
Definition	I-Device
Language	I-Device
)	O
compiler	O
generated	O
the	O
DCP	O
code	O
and	O
NDF	O
(	O
network	O
definition	O
file	O
)	O
.	O
</s>
<s>
There	O
was	O
one	O
ALGOL	B-Language
function	O
for	O
each	O
kind	O
of	O
DCP	O
instruction	O
,	O
and	O
if	O
you	O
called	O
that	O
function	O
then	O
the	O
corresponding	O
DCP	O
instruction	O
bits	O
would	O
be	O
emitted	O
to	O
the	O
output	O
.	O
</s>
<s>
A	O
DCP	O
program	O
was	O
an	O
ALGOL	B-Language
program	O
comprising	O
nothing	O
but	O
a	O
long	O
list	O
of	O
calls	O
on	O
these	O
functions	O
,	O
one	O
for	O
each	O
assembly	B-Language
language	I-Language
statement	O
.	O
</s>
<s>
Essentially	O
ALGOL	B-Language
acted	O
like	O
the	O
macro	O
pass	O
of	O
a	O
macro	O
assembler	B-Language
.	O
</s>
<s>
The	O
first	O
pass	O
was	O
the	O
ALGOL	B-Language
compiler	O
;	O
the	O
second	O
pass	O
was	O
running	O
the	O
resulting	O
program	O
(	O
on	O
the	O
B6500	O
)	O
which	O
would	O
then	O
emit	O
the	O
binary	O
for	O
the	O
DCP	O
.	O
</s>
<s>
Another	O
variant	O
of	O
ALGOL	B-Language
is	O
DMALGOL	O
(	O
Data	O
Management	O
ALGOL	B-Language
)	O
.	O
</s>
<s>
DMALGOL	O
is	O
ALGOL	B-Language
extended	O
for	O
compiling	O
the	O
DMSII	B-Application
database	O
software	O
from	O
database	O
description	O
files	O
created	O
by	O
the	O
DASDL	O
(	O
Data	O
Access	O
and	O
Structure	O
Definition	O
Language	O
)	O
compiler	O
.	O
</s>
<s>
Normal	O
user-level	O
programs	O
obtain	O
database	O
access	O
by	O
using	O
code	O
written	O
in	O
application	O
languages	O
,	O
mainly	O
ALGOL	B-Language
and	O
COBOL	B-Application
,	O
extended	O
with	O
database	O
instructions	O
and	O
transaction	O
processing	O
directives	O
.	O
</s>
<s>
DMALGOL	O
is	O
used	O
to	O
provide	O
tailored	O
access	O
routines	O
for	O
DMSII	B-Application
databases	O
.	O
</s>
<s>
Also	O
the	O
verbs	O
"	O
begintransaction	O
"	O
and	O
"	O
endtransaction	O
"	O
were	O
included	O
,	O
solving	O
the	O
deadlock	B-Operating_System
situation	O
when	O
multiple	O
processes	O
accessed	O
and	O
updated	O
the	O
same	O
structures	O
.	O
</s>
<s>
Roy	O
Guck	O
of	O
Burroughs	O
was	O
one	O
of	O
the	O
main	O
developers	O
of	O
DMSII	B-Application
.	O
</s>
<s>
In	O
later	O
years	O
,	O
with	O
compiler	O
code	O
size	O
being	O
less	O
of	O
a	O
concern	O
,	O
most	O
of	O
the	O
preprocessing	O
constructs	O
were	O
made	O
available	O
in	O
the	O
user	O
level	O
of	O
ALGOL	B-Language
.	O
</s>
<s>
The	O
B5000	O
was	O
designed	O
as	O
a	O
stack	B-Application
machine	I-Application
–	O
all	O
program	O
data	O
except	O
for	O
arrays	O
(	O
which	O
include	O
strings	O
and	O
objects	O
)	O
was	O
kept	O
on	O
the	O
stack	O
.	O
</s>
<s>
Multitasking	B-Operating_System
is	O
also	O
very	O
efficient	O
on	O
the	O
B5000	O
and	O
B6500	O
lines	O
.	O
</s>
<s>
Each	O
stack	O
and	O
associated	O
Program	O
Reference	O
Table	O
(	O
PRT	O
)	O
represents	O
a	O
process	O
(	O
task	O
or	O
thread	O
)	O
and	O
tasks	O
can	O
become	O
blocked	O
waiting	O
on	O
resource	O
requests	O
(	O
which	O
includes	O
waiting	O
for	O
a	O
processor	O
to	O
run	O
on	O
if	O
the	O
task	O
has	O
been	O
interrupted	O
because	O
of	O
preemptive	O
multitasking	B-Operating_System
)	O
.	O
</s>
<s>
User	O
programs	O
cannot	O
issue	O
an	O
IP1	O
,	O
IP2	O
or	O
MVST	O
,	O
and	O
there	O
is	O
only	O
one	O
place	O
in	O
the	O
operating	B-General_Concept
system	I-General_Concept
where	O
this	O
is	O
done	O
.	O
</s>
<s>
The	O
operating	B-General_Concept
system	I-General_Concept
code	O
is	O
entered	O
and	O
run	O
on	O
top	O
of	O
the	O
user	O
stack	O
.	O
</s>
<s>
The	O
operating	B-General_Concept
system	I-General_Concept
determines	O
the	O
first	O
process	O
in	O
the	O
ready	O
queue	O
and	O
invokes	O
the	O
instruction	O
move_stack	O
,	O
which	O
makes	O
the	O
process	O
at	O
the	O
head	O
of	O
the	O
ready	O
queue	O
active	O
.	O
</s>
<s>
Stack	O
performance	O
was	O
considered	O
to	O
be	O
slow	O
compared	O
to	O
register-based	O
architectures	O
,	O
for	O
example	O
,	O
such	O
an	O
architecture	O
had	O
been	O
considered	O
and	O
rejected	O
for	O
the	O
System/360	B-Application
.	O
</s>
<s>
In	O
fact	O
,	O
the	O
A	O
Series	O
line	O
of	O
B5000	O
successors	O
included	O
the	O
first	O
single	O
chip	O
mainframe	B-Architecture
,	O
the	O
Micro-A	O
of	O
the	O
late	O
1980s	O
.	O
</s>
<s>
This	O
"	O
mainframe	B-Architecture
"	O
chip	O
(	O
named	O
SCAMP	O
for	O
Single-Chip	O
A-series	O
Mainframe	B-Architecture
Processor	O
)	O
sat	O
on	O
an	O
Intel-based	O
plug-in	O
PC	O
board	O
.	O
</s>
<s>
—	O
This	O
is	O
lexical	O
level	O
2	O
(	O
level	O
zero	O
is	O
reserved	O
for	O
the	O
operating	B-General_Concept
system	I-General_Concept
and	O
level	O
1	O
for	O
code	O
segments	O
)	O
.	O
</s>
<s>
The	O
visibility	O
rules	O
of	O
ALGOL	B-Language
,	O
a	O
language	O
designed	O
for	O
single	O
pass	O
compilers	O
,	O
mean	O
that	O
only	O
variables	O
declared	O
before	O
the	O
current	O
position	O
are	O
visible	O
at	O
that	O
part	O
of	O
the	O
code	O
,	O
thus	O
the	O
requirement	O
for	O
forward	O
declarations	O
.	O
</s>
<s>
so	O
it	O
is	O
very	O
rare	O
to	O
find	O
a	O
procedure	O
nested	O
more	O
than	O
five	O
levels	O
deep	O
,	O
and	O
it	O
could	O
be	O
argued	O
that	O
such	O
programs	O
would	O
be	O
poorly	O
structured	B-Language
.	O
</s>
<s>
This	O
could	O
cause	O
difficulty	O
for	O
some	O
systems	O
that	O
generated	O
Algol	B-Language
source	O
as	O
output	O
(	O
tailored	O
to	O
solve	O
some	O
special	O
problem	O
)	O
if	O
the	O
generation	O
method	O
frequently	O
nested	O
procedure	O
within	O
procedure	O
.	O
</s>
<s>
This	O
EVENT	O
mechanism	O
is	O
a	O
basic	O
enabler	O
for	O
multiprocessing	B-Operating_System
in	O
addition	O
to	O
multitasking	B-Operating_System
.	O
</s>
<s>
Thus	O
Burroughs	O
Extended	O
ALGOL	B-Language
had	O
some	O
of	O
the	O
multi-processing	B-Operating_System
and	O
synchronization	O
features	O
of	O
later	O
languages	O
like	O
Ada	B-Language
.	O
</s>
<s>
Inline	O
functions	O
are	O
similar	O
to	O
parameterized	O
macros	O
such	O
as	O
C	B-Language
#defines	B-Language
,	O
except	O
you	O
do	O
n't	O
get	O
the	O
problems	O
with	O
parameters	O
that	O
you	O
can	O
with	O
macros	O
.	O
</s>
<s>
This	O
facility	O
is	O
available	O
in	O
NEWP	B-Language
.	O
</s>
<s>
This	O
means	O
that	O
asynchronous	O
processes	O
still	O
have	O
access	O
to	O
the	O
D[2]	O
environment	O
as	O
implied	O
in	O
ALGOL	B-Language
program	O
code	O
.	O
</s>
<s>
The	O
D[0]	O
environment	O
represents	O
entities	O
exported	O
by	O
the	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Arrays	O
were	O
not	O
stored	O
in	O
this	O
area	O
,	O
only	O
a	O
one	O
word	O
descriptor	B-Device
for	O
the	O
array	O
was	O
.	O
</s>
<s>
Further	O
,	O
only	O
the	O
VALC	O
opcode	O
loaded	O
data	O
:	O
opcodes	O
for	O
ADD	O
,	O
MULT	O
and	O
so	O
forth	B-Application
did	O
no	O
addressing	O
,	O
working	O
entirely	O
on	O
the	O
top	O
elements	O
of	O
the	O
stack	O
.	O
</s>
<s>
Similarly	O
,	O
within	O
a	O
task	O
,	O
an	O
array	O
descriptor	B-Device
contained	O
information	O
on	O
the	O
array	O
's	O
bounds	O
,	O
and	O
so	O
any	O
indexing	O
operation	O
was	O
checked	O
by	O
the	O
hardware	O
:	O
put	O
another	O
way	O
,	O
each	O
array	O
formed	O
its	O
own	O
address	O
space	O
.	O
</s>
<s>
In	O
any	O
case	O
,	O
the	O
tagging	O
of	O
all	O
memory	O
words	O
provided	O
a	O
second	O
level	O
of	O
protection	O
:	O
a	O
misdirected	O
assignment	O
of	O
a	O
value	O
could	O
only	O
go	O
to	O
a	O
data-holding	O
location	O
,	O
not	O
to	O
one	O
holding	O
a	O
pointer	O
or	O
an	O
array	O
descriptor	B-Device
,	O
etc	O
.	O
</s>
<s>
Arrays	O
were	O
not	O
stored	O
contiguous	O
in	O
memory	O
with	O
other	O
variables	O
,	O
they	O
were	O
each	O
granted	O
their	O
own	O
address	O
space	O
,	O
which	O
was	O
located	O
via	O
the	O
descriptor	B-Device
.	O
</s>
<s>
In	O
ALGOL	B-Language
's	O
case	O
,	O
a	O
multidimensional	O
array	O
would	O
employ	O
multiple	O
levels	O
of	O
such	O
addressing	O
.	O
</s>
<s>
For	O
a	O
reference	O
to	O
A(i,j )	O
,	O
the	O
first	O
index	O
would	O
be	O
into	O
an	O
array	O
of	O
descriptors	O
,	O
one	O
descriptor	B-Device
for	O
each	O
of	O
the	O
rows	O
of	O
A	O
,	O
which	O
row	O
would	O
then	O
be	O
indexed	O
with	O
j	O
as	O
for	O
a	O
single-dimensional	O
array	O
,	O
and	O
so	O
on	O
for	O
higher	O
dimensions	O
.	O
</s>
<s>
FORTRAN	B-Application
however	O
regards	O
all	O
multidimensional	O
arrays	O
as	O
being	O
equivalent	O
to	O
a	O
single-dimensional	O
array	O
of	O
the	O
same	O
size	O
,	O
and	O
for	O
a	O
multidimensional	O
array	O
simple	O
integer	O
arithmetic	O
is	O
used	O
to	O
calculate	O
the	O
offset	O
where	O
element	O
A(i,j,k )	O
would	O
be	O
found	O
in	O
that	O
single	O
sequence	O
.	O
</s>
<s>
The	O
single-dimensional	O
equivalent	O
array	O
,	O
possibly	O
segmented	O
if	O
large	O
enough	O
,	O
would	O
then	O
be	O
accessed	O
in	O
the	O
same	O
manner	O
as	O
a	O
single-dimensional	O
array	O
in	O
ALGOL	B-Language
.	O
</s>
<s>
In	O
ALGOL	B-Language
's	O
case	O
,	O
this	O
enabled	O
the	O
development	O
of	O
"	O
ragged	O
"	O
arrays	O
,	O
rather	O
than	O
the	O
usual	O
fixed	O
rectangular	O
(	O
or	O
higher	O
dimension	O
)	O
arrays	O
.	O
</s>
<s>
FORTRAN	B-Application
was	O
not	O
expected	O
to	O
support	O
recursion	O
and	O
perhaps	O
one	O
stumbling	O
block	O
to	O
people	O
's	O
understanding	O
of	O
how	O
ALGOL	B-Language
was	O
to	O
be	O
implemented	O
was	O
how	O
to	O
implement	O
recursion	O
.	O
</s>
<s>
The	O
Burroughs	O
FORTRAN	B-Application
compiler	O
allowed	O
recursive	O
calls	O
(	O
just	O
as	O
every	O
other	O
FORTRAN	B-Application
compiler	O
does	O
)	O
,	O
but	O
unlike	O
many	O
other	O
computers	O
,	O
on	O
a	O
stack-based	O
system	O
the	O
returns	O
from	O
such	O
calls	O
succeeded	O
as	O
well	O
.	O
</s>
<s>
Thus	O
Burroughs	O
FORTRAN	B-Application
had	O
better	O
error	O
checking	O
than	O
other	O
contemporary	O
implementation	O
of	O
FORTRAN	B-Application
.	O
</s>
<s>
For	O
instance	O
,	O
for	O
subroutines	O
and	O
functions	O
it	O
checked	O
that	O
they	O
were	O
invoked	O
with	O
the	O
correct	O
number	O
of	O
parameters	O
,	O
as	O
is	O
normal	O
for	O
ALGOL-style	O
compilers	O
.	O
</s>
<s>
In	O
fact	O
,	O
Burroughs	O
became	O
known	O
for	O
its	O
superior	O
compilers	O
and	O
implementation	O
of	O
languages	O
,	O
including	O
the	O
object-oriented	B-Language
Simula	B-Language
(	O
a	O
superset	O
of	O
ALGOL	B-Language
)	O
,	O
and	O
Iverson	O
,	O
the	O
designer	O
of	O
APL	B-Language
declared	O
that	O
the	O
Burroughs	O
implementation	O
of	O
APL	B-Language
was	O
the	O
best	O
he	O
'd	O
seen	O
.	O
</s>
<s>
John	O
McCarthy	O
,	O
the	O
language	O
designer	O
of	O
LISP	B-Language
disagreed	O
,	O
since	O
LISP	B-Language
was	O
based	O
on	O
modifiable	O
code	O
,	O
he	O
did	O
not	O
like	O
the	O
unmodifiable	O
code	O
of	O
the	O
B5000	O
,	O
but	O
most	O
LISP	B-Language
implementations	O
would	O
run	O
in	O
an	O
interpretive	O
environment	O
anyway	O
.	O
</s>
<s>
The	O
most	O
defining	O
aspect	O
of	O
the	O
B5000	O
is	O
that	O
it	O
is	O
a	O
stack	B-Application
machine	I-Application
as	O
treated	O
above	O
.	O
</s>
<s>
However	O
,	O
two	O
other	O
very	O
important	O
features	O
of	O
the	O
architecture	O
is	O
that	O
it	O
is	O
tag-based	B-Architecture
and	O
descriptor-based	O
.	O
</s>
<s>
Later	O
,	O
when	O
the	O
B6500	O
was	O
designed	O
,	O
it	O
was	O
realized	O
that	O
the	O
1-bit	O
control	O
word/numeric	O
distinction	O
was	O
a	O
powerful	O
idea	O
and	O
this	O
was	O
extended	O
to	O
three	O
bits	O
outside	O
of	O
the	O
48	O
bit	O
word	O
into	O
a	O
tag	B-Architecture
.	O
</s>
<s>
The	O
data	O
bits	O
are	O
bits	O
0	O
–	O
47	O
and	O
the	O
tag	B-Architecture
is	O
in	O
bits	O
48	O
–	O
50	O
.	O
</s>
<s>
Code	O
words	O
were	O
given	O
tag	B-Architecture
3	O
.	O
</s>
<s>
Internally	O
,	O
some	O
of	O
the	O
machines	O
had	O
60	O
bit	O
words	O
,	O
with	O
the	O
extra	O
bits	O
being	O
used	O
for	O
engineering	O
purposes	O
such	O
as	O
a	O
Hamming	B-Error_Name
code	I-Error_Name
error-correction	O
field	O
,	O
but	O
these	O
were	O
never	O
seen	O
by	O
programmers	O
.	O
</s>
<s>
The	O
current	O
incarnation	O
of	O
these	O
machines	O
,	O
the	O
Unisys	O
ClearPath	O
has	O
extended	O
tags	O
further	O
into	O
a	O
four	O
bit	O
tag	B-Architecture
.	O
</s>
<s>
Even-tagged	O
words	O
are	O
user	O
data	O
which	O
can	O
be	O
modified	O
by	O
a	O
user	O
program	O
as	O
user	O
state	O
.	O
</s>
<s>
Odd-tagged	O
words	O
are	O
created	O
and	O
used	O
directly	O
by	O
the	O
hardware	O
and	O
represent	O
a	O
program	O
's	O
execution	O
state	O
.	O
</s>
<s>
Tag	B-Architecture
1	O
words	O
represent	O
on-stack	O
data	O
addresses	O
.	O
</s>
<s>
Tag	B-Architecture
5	O
words	O
are	O
descriptors	O
,	O
which	O
are	O
more	O
fully	O
described	O
in	O
the	O
next	O
section	O
.	O
</s>
<s>
Tag	B-Architecture
5	O
words	O
represent	O
off-stack	O
data	O
addresses	O
.	O
</s>
<s>
Tag	B-Architecture
7	O
is	O
the	O
program	O
control	O
word	O
which	O
describes	O
a	O
procedure	O
entry	O
point	O
.	O
</s>
<s>
Thus	O
code	O
is	O
reentrant	B-Operating_System
and	O
shared	O
.	O
</s>
<s>
Tag	B-Architecture
3	O
represents	O
code	O
words	O
themselves	O
,	O
which	O
wo	O
n't	O
occur	O
on	O
the	O
stack	O
.	O
</s>
<s>
Tag	B-Architecture
3	O
is	O
also	O
used	O
for	O
the	O
stack	O
control	O
words	O
MSCW	O
,	O
RCW	O
,	O
TOSCW	O
.	O
</s>
<s>
The	O
figure	O
to	O
the	O
left	O
shows	O
how	O
the	O
Burroughs	O
Large	O
System	O
architecture	O
was	O
fundamentally	O
a	O
hardware	O
architecture	O
for	O
object-oriented	B-Language
programming	I-Language
,	O
something	O
that	O
still	O
does	O
n't	O
exist	O
in	O
conventional	O
architectures	O
.	O
</s>
<s>
There	O
are	O
three	O
distinct	O
instruction	B-General_Concept
sets	I-General_Concept
for	O
the	O
Burroughs	B-Device
large	I-Device
systems	I-Device
.	O
</s>
<s>
All	O
three	O
are	O
based	O
on	O
short	O
syllables	B-General_Concept
that	O
fit	O
evenly	O
into	O
words	O
.	O
</s>
<s>
Programs	O
on	O
a	O
B5000	O
,	O
B5500	O
and	O
B5700	O
are	O
made	O
up	O
of	O
12-bit	B-General_Concept
syllables	I-General_Concept
,	O
four	O
to	O
a	O
word	O
.	O
</s>
<s>
The	O
architecture	O
has	O
two	O
modes	O
,	O
Word	O
Mode	O
and	O
Character	O
Mode	O
,	O
and	O
each	O
has	O
a	O
separate	O
repertoire	O
of	O
syllables	B-General_Concept
.	O
</s>
<s>
A	O
processor	O
may	O
be	O
either	O
Control	O
State	O
or	O
Normal	O
State	O
,	O
and	O
certain	O
syllables	B-General_Concept
are	O
only	O
permissible	O
in	O
Control	O
State	O
.	O
</s>
<s>
Programs	O
are	O
made	O
up	O
of	O
8-bit	O
syllables	B-General_Concept
,	O
which	O
may	O
be	O
Name	O
Call	O
,	O
be	O
Value	O
Call	O
or	O
form	O
an	O
operator	O
,	O
which	O
may	O
be	O
from	O
one	O
to	O
twelve	O
syllables	B-General_Concept
in	O
length	O
.	O
</s>
<s>
There	O
are	O
less	O
than	O
200	O
operators	O
,	O
all	O
of	O
which	O
fit	O
into	O
8-bit	O
syllables	B-General_Concept
.	O
</s>
<s>
Many	O
of	O
these	O
operators	O
are	O
polymorphic	B-Application
depending	O
on	O
the	O
kind	O
of	O
data	O
being	O
acted	O
on	O
as	O
given	O
by	O
the	O
tag	B-Architecture
.	O
</s>
<s>
If	O
we	O
remove	O
the	O
operators	O
reserved	O
for	O
the	O
operating	B-General_Concept
system	I-General_Concept
such	O
as	O
MVST	O
and	O
HALT	O
,	O
the	O
set	O
of	O
operators	O
commonly	O
used	O
by	O
user-level	O
programs	O
is	O
less	O
than	O
100	O
.	O
</s>
<s>
The	O
Name	O
Call	O
and	O
Value	O
Call	O
syllables	B-General_Concept
contain	O
address	O
couples	O
;	O
the	O
Operator	O
syllables	B-General_Concept
either	O
use	O
no	O
addresses	O
or	O
use	O
control	O
words	O
and	O
descriptors	O
on	O
the	O
stack	O
.	O
</s>
<s>
The	O
Algol	B-Language
compiler	O
produced	O
code	O
to	O
invoke	O
this	O
operator	O
via	O
a	O
special	O
function	O
that	O
enabled	O
a	O
"	O
swap	O
"	O
operation	O
on	O
single-word	O
data	O
without	O
an	O
explicit	O
temporary	O
value	O
.	O
</s>
<s>
Two	O
processors	O
could	O
infrequently	O
simultaneously	O
send	O
each	O
other	O
a	O
'	O
HEYU	O
 '	O
command	O
resulting	O
in	O
a	O
lockup	O
known	O
as	O
'	O
a	O
deadly	B-Operating_System
embrace	I-Operating_System
 '	O
.	O
</s>
<s>
The	O
direct	O
influence	O
of	O
the	O
B5000	O
can	O
be	O
seen	O
in	O
the	O
current	O
Unisys	O
ClearPath	O
range	O
of	O
mainframes	B-Architecture
which	O
are	O
the	O
direct	O
descendants	O
of	O
the	O
B6500	O
,	O
which	O
was	O
influenced	O
by	O
the	O
B5000	O
,	O
and	O
still	O
have	O
the	O
MCP	B-Application
operating	B-General_Concept
system	I-General_Concept
after	O
40	O
years	O
of	O
consistent	O
development	O
.	O
</s>
<s>
This	O
architecture	O
is	O
now	O
called	O
emode	O
(	O
for	O
emulation	O
mode	O
)	O
since	O
the	O
B6500	O
architecture	O
has	O
been	O
implemented	O
on	O
machines	O
built	O
from	O
Intel	B-Device
Xeon	I-Device
processors	O
running	O
the	O
x86	B-Operating_System
instruction	B-General_Concept
set	I-General_Concept
as	O
the	O
native	O
instruction	B-General_Concept
set	I-General_Concept
,	O
with	O
code	O
running	O
on	O
those	O
processors	O
emulating	O
the	O
B5000	O
instruction	B-General_Concept
set	I-General_Concept
.	O
</s>
<s>
In	O
those	O
machines	O
,	O
there	O
was	O
also	O
going	O
to	O
be	O
an	O
nmode	O
(	O
native	B-Language
mode	I-Language
)	O
,	O
but	O
this	O
was	O
dropped	O
,	O
so	O
you	O
may	O
often	O
hear	O
the	O
B6500	O
successor	O
machines	O
being	O
referred	O
to	O
as	O
"	O
emode	O
machines	O
"	O
.	O
</s>
<s>
B5000	O
machines	O
were	O
programmed	O
exclusively	O
in	O
high-level	B-Language
languages	I-Language
;	O
there	O
is	O
no	O
assembler	B-Language
.	O
</s>
<s>
The	O
B5000	O
stack	B-Application
architecture	I-Application
inspired	O
Chuck	O
Moore	O
,	O
the	O
designer	O
of	O
the	O
programming	O
language	O
Forth	B-Application
,	O
who	O
encountered	O
the	O
B5500	O
while	O
at	O
MIT	O
.	O
</s>
<s>
In	O
,	O
Moore	O
described	O
the	O
influence	O
,	O
noting	O
that	O
Forth	B-Application
's	O
DUP	O
,	O
DROP	O
and	O
SWAP	O
came	O
from	O
the	O
corresponding	O
B5500	O
instructions	O
(	O
DUPL	O
,	O
DLET	O
,	O
EXCH	O
)	O
.	O
</s>
<s>
B5000	O
machines	O
with	O
their	O
stack-based	O
architecture	O
and	O
tagged	B-Architecture
memory	O
also	O
heavily	O
influenced	O
the	O
Soviet	O
Elbrus	B-Device
series	O
of	O
mainframes	B-Architecture
and	O
supercomputers	B-Architecture
.	O
</s>
<s>
The	O
first	O
two	O
generations	O
of	O
the	O
series	O
featured	O
tagged	B-Architecture
memory	O
and	O
stack-based	O
CPUs	O
that	O
were	O
programmed	O
only	O
in	O
high-level	B-Language
languages	I-Language
.	O
</s>
<s>
There	O
existed	O
a	O
kind	O
of	O
an	O
assembly	B-Language
language	I-Language
for	O
them	O
,	O
called	O
El-76	O
,	O
but	O
it	O
was	O
more	O
or	O
less	O
a	O
modification	O
of	O
ALGOL	B-Language
68	I-Language
and	O
supported	O
structured	B-Language
programming	I-Language
and	O
first-class	O
procedures	O
.	O
</s>
<s>
Later	O
generations	O
of	O
the	O
series	O
,	O
though	O
,	O
switched	O
away	O
from	O
this	O
architecture	O
to	O
the	O
EPIC-like	O
VLIW	B-General_Concept
CPUs	I-General_Concept
.	O
</s>
<s>
The	O
Hewlett-Packard	O
designers	O
of	O
the	O
HP	B-Device
3000	I-Device
business	O
system	O
had	O
used	O
a	O
B5500	O
and	O
were	O
greatly	O
impressed	O
by	O
its	O
hardware	O
and	O
software	O
;	O
they	O
aimed	O
to	O
build	O
a	O
16-bit	O
minicomputer	O
with	O
similar	O
software	O
.	O
</s>
<s>
Several	O
other	O
HP	O
divisions	O
created	O
similar	O
minicomputer	O
or	O
microprocessor	O
stack	B-Application
machines	I-Application
.	O
</s>
<s>
Bob	O
Barton	O
's	O
work	O
on	O
reverse	B-Application
Polish	I-Application
notation	O
(	O
RPN	O
)	O
also	O
found	O
its	O
way	O
into	O
HP	B-Device
calculators	I-Device
beginning	O
with	O
the	O
9100A	O
,	O
and	O
notably	O
the	O
HP-35	B-Device
and	O
subsequent	O
calculators	O
.	O
</s>
<s>
The	O
NonStop	O
systems	O
designed	O
by	O
Tandem	O
Computers	O
in	O
the	O
late	O
1970s	O
and	O
early	O
1980s	O
were	O
also	O
16-bit	O
stack	B-Application
machines	I-Application
,	O
influenced	O
by	O
the	O
B5000	O
indirectly	O
through	O
the	O
HP	B-Device
3000	I-Device
connection	O
,	O
as	O
several	O
of	O
the	O
early	O
Tandem	O
engineers	O
were	O
formerly	O
with	O
HP	O
.	O
</s>
<s>
Around	O
1990	O
,	O
these	O
systems	O
migrated	O
to	O
MIPS	O
RISC	O
architecture	O
but	O
continued	O
to	O
support	O
execution	O
of	O
stack	B-Application
machine	I-Application
binaries	O
by	O
object	O
code	O
translation	O
or	O
direct	O
emulation	O
.	O
</s>
<s>
Sometime	O
after	O
2000	O
,	O
these	O
systems	O
migrated	O
to	O
Itanium	B-General_Concept
architecture	O
and	O
continued	O
to	O
run	O
the	O
legacy	O
stack	B-Application
machine	I-Application
binaries	O
.	O
</s>
<s>
Kay	O
was	O
also	O
impressed	O
by	O
the	O
data-driven	O
tagged	B-Architecture
architecture	I-Architecture
of	O
the	O
B5000	O
and	O
this	O
influenced	O
his	O
thinking	O
in	O
his	O
developments	O
in	O
object-oriented	B-Language
programming	I-Language
and	O
Smalltalk	B-Application
.	O
</s>
<s>
The	O
value	O
of	O
the	O
hardware-architecture	O
binding	O
that	O
existed	O
before	O
emode	O
would	O
be	O
substantially	O
preserved	O
in	O
the	O
x86-based	O
machines	O
to	O
the	O
extent	O
that	O
MCP	B-Application
was	O
the	O
one	O
and	O
only	O
control	O
program	O
,	O
but	O
the	O
support	O
provided	O
by	O
those	O
machines	O
is	O
still	O
inferior	O
to	O
that	O
provided	O
on	O
the	O
machines	O
where	O
the	O
B6500	O
instruction	B-General_Concept
set	I-General_Concept
is	O
the	O
native	O
instruction	B-General_Concept
set	I-General_Concept
.	O
</s>
<s>
A	O
little-known	O
Intel	O
processor	O
architecture	O
that	O
actually	O
preceded	O
32-bit	O
implementations	O
of	O
the	O
x86	B-Operating_System
instruction	B-General_Concept
set	I-General_Concept
,	O
the	O
Intel	B-Device
iAPX	I-Device
432	I-Device
,	O
would	O
have	O
provided	O
an	O
equivalent	O
physical	O
basis	O
,	O
as	O
it	O
too	O
was	O
essentially	O
an	O
object-oriented	B-Language
architecture	O
.	O
</s>
