<s>
''	O
This	O
article	O
refers	O
the	O
mainframe	B-Architecture
text	B-Application
editor	I-Application
.	O
</s>
<s>
CANDE	B-Operating_System
(	O
Command	O
AND	O
Edit	O
)	O
is	O
a	O
command	B-Application
line	I-Application
shell	B-Operating_System
and	O
text	B-Application
editor	I-Application
on	O
the	O
MCP	B-Application
(	O
Master	B-Application
Control	I-Application
Program	I-Application
)	O
operating	B-General_Concept
system	I-General_Concept
which	O
runs	O
on	O
the	O
Unisys	O
Clearpath	O
series	O
of	O
mainframes	B-Architecture
.	O
</s>
<s>
Originally	O
implemented	O
on	O
Burroughs	B-Device
large	I-Device
systems	I-Device
,	O
it	O
has	O
a	O
range	O
of	O
features	O
for	O
interacting	O
with	O
the	O
operating	B-General_Concept
system	I-General_Concept
execution	O
environment	O
,	O
focused	O
on	O
executing	O
,	O
editing	O
and	O
compiling	O
programs	O
,	O
and	O
creating	O
,	O
copying	O
,	O
moving	O
,	O
renaming	O
,	O
and	O
deleting	O
files	O
in	O
general	O
.	O
</s>
<s>
Its	O
full	O
name	O
is	O
CANDE	B-Operating_System
MCS	O
.	O
</s>
<s>
MCS	O
,	O
or	O
Message	O
Control	O
Subsystem	O
is	O
the	O
general	O
form	O
of	O
a	O
systems	O
program	O
in	O
the	O
Burroughs	O
architecture	O
(	O
other	O
than	O
MCP	B-Application
,	O
the	O
Master	B-Application
Control	I-Application
Program	I-Application
or	O
core	O
OS	O
)	O
.	O
</s>
<s>
As	O
an	O
MCS	O
,	O
CANDE	B-Operating_System
is	O
more	O
than	O
just	O
an	O
editor	O
as	O
it	O
provides	O
overall	O
control	O
for	O
a	O
network	O
of	O
users	O
.	O
</s>
<s>
The	O
editing	O
capabilities	O
of	O
CANDE	B-Operating_System
are	O
anachronistic	O
for	O
casual	O
(	O
as	O
opposed	O
to	O
scripted	O
)	O
editing	O
as	O
they	O
predate	O
full	O
screen	O
and	O
graphical	O
editors	O
.	O
</s>
<s>
CANDE	B-Operating_System
was	O
also	O
used	O
on	O
the	O
Burroughs	O
CMS	O
(	O
mini	O
computer	O
)	O
range	O
,	O
with	O
very	O
similar	O
syntax	O
.	O
</s>
<s>
In	O
contemporary	O
MCP	B-Application
,	O
CANDE	B-Operating_System
is	O
primarily	O
used	O
thru	O
the	O
ODT	O
(	O
Operator	O
Display	O
Terminal	O
)	O
and	O
MARC	O
(	O
Menu	O
Assisted	O
Resource	O
Control	O
)	O
on	O
emulators	O
of	O
the	O
original	O
character	O
oriented	O
terminals	O
as	O
with	O
other	O
legacy	O
mainframe	B-Architecture
interfaces	O
such	O
as	O
ISPF	B-Operating_System
.	O
</s>
<s>
CANDE	B-Operating_System
provides	O
a	O
command-line	B-Application
interpreter	O
and	O
line	B-Application
editor	I-Application
,	O
although	O
unlike	O
the	O
modern	O
interpretation	O
of	O
an	O
operating	B-General_Concept
system	I-General_Concept
command	B-Application
line	I-Application
interpreter	O
,	O
the	O
CANDE	B-Operating_System
commands	O
are	O
compiled	O
into	O
the	O
CANDE	B-Operating_System
MCS	O
,	O
as	O
shell	B-Operating_System
like	O
capabilities	O
are	O
provided	O
by	O
WFL	B-Language
.	O
</s>
<s>
In	O
addition	O
to	O
these	O
features	O
CANDE	B-Operating_System
has	O
an	O
on-line	O
help	O
facility	O
.	O
</s>
<s>
For	O
extra	O
speed	O
,	O
CANDE	B-Operating_System
implemented	O
user	O
context	O
switching	O
by	O
swapping	O
a	O
block	O
at	O
the	O
top	O
of	O
the	O
stack	O
.	O
</s>
<s>
This	O
novel	O
method	O
broke	O
several	O
assumptions	O
built	O
into	O
the	O
design	O
of	O
Burroughs	B-Device
large	I-Device
systems	I-Device
,	O
in	O
particular	O
the	O
handling	O
of	O
virtual	O
memory	O
descriptors	O
,	O
and	O
meant	O
that	O
CANDE	B-Operating_System
itself	O
had	O
to	O
be	O
written	O
in	O
DCALGOL	O
with	O
system-level	O
privileges	O
.	O
</s>
<s>
Architecturally	O
,	O
CANDE	B-Operating_System
is	O
split	O
into	O
two	O
main	O
sections	O
:	O
a	O
primary	O
,	O
single-instanced	O
main	O
process	O
originally	O
supporting	O
up	O
to	O
255	O
simultaneous	O
users	O
,	O
and	O
one	O
or	O
more	O
worker	O
stacks	O
.	O
</s>
<s>
CANDE	B-Operating_System
operates	O
without	O
internal	O
locks	O
,	O
by	O
careful	O
separation	O
of	O
data	O
.	O
</s>
<s>
This	O
allows	O
CANDE	B-Operating_System
to	O
index	O
into	O
the	O
array	O
using	O
only	O
addition	O
,	O
not	O
multiplication	O
(	O
which	O
made	O
for	O
faster	O
operation	O
on	O
the	O
hard-wired	O
CPUs	O
of	O
the	O
era	O
)	O
.	O
</s>
<s>
CANDE	B-Operating_System
was	O
originally	O
written	O
in	O
1973	O
by	O
Darrel	B-Operating_System
F	I-Operating_System
.	I-Operating_System
High	I-Operating_System
.	O
</s>
