<s>
A	O
front	B-Device
panel	I-Device
was	O
used	O
on	O
early	O
electronic	O
computers	O
to	O
display	O
and	O
allow	O
the	O
alteration	O
of	O
the	O
state	O
of	O
the	O
machine	O
's	O
internal	O
registers	B-General_Concept
and	O
memory	B-General_Concept
.	O
</s>
<s>
The	O
front	B-Device
panel	I-Device
usually	O
consisted	O
of	O
arrays	O
of	O
indicator	O
lamps	O
,	O
digit	O
and	O
symbol	O
displays	O
,	O
toggle	O
switches	O
,	O
dials	O
,	O
and	O
push	O
buttons	O
mounted	O
on	O
a	O
sheet	O
metal	O
face	O
plate	O
.	O
</s>
<s>
In	O
early	O
machines	O
,	O
CRTs	O
might	O
also	O
be	O
present	O
(	O
as	O
an	O
oscilloscope	O
,	O
or	O
,	O
for	O
example	O
,	O
to	O
mirror	O
the	O
contents	O
of	O
Williams	B-General_Concept
–	I-General_Concept
Kilburn	I-General_Concept
tube	I-General_Concept
memory	B-General_Concept
)	O
.	O
</s>
<s>
Prior	O
to	O
the	O
development	O
of	O
CRT	B-Device
system	B-Device
consoles	I-Device
,	O
</s>
<s>
many	O
computers	O
such	O
as	O
the	O
IBM	B-Device
1620	I-Device
had	O
console	O
typewriters	O
.	O
</s>
<s>
Usually	O
the	O
contents	O
of	O
one	O
or	O
more	O
hardware	B-General_Concept
registers	I-General_Concept
would	O
be	O
represented	O
by	O
a	O
row	O
of	O
lights	O
,	O
allowing	O
the	O
contents	O
to	O
be	O
read	O
directly	O
when	O
the	O
machine	O
was	O
stopped	O
.	O
</s>
<s>
The	O
switches	O
allowed	O
direct	O
entry	O
of	O
data	O
and	O
address	O
values	O
into	O
registers	B-General_Concept
or	O
memory	B-General_Concept
.	O
</s>
<s>
These	O
were	O
often	O
referred	O
to	O
as	O
sense	O
indicators	O
,	O
sense	O
lights	O
and	O
sense	B-Device
switches	I-Device
.	O
</s>
<s>
For	O
example	O
,	O
the	O
original	O
Fortran	B-Application
compiler	O
for	O
the	O
IBM	B-Device
704	I-Device
contained	O
specific	O
statements	O
for	O
testing	O
and	O
manipulation	O
of	O
the	O
704	O
's	O
sense	O
lights	O
and	O
switches	O
.	O
</s>
<s>
These	O
switches	O
were	O
often	O
used	O
by	O
the	O
program	O
to	O
control	O
optional	O
behavior	O
,	O
for	O
example	O
information	O
might	O
be	O
printed	O
only	O
if	O
a	O
particular	O
sense	B-Device
switch	I-Device
was	O
set	O
.	O
</s>
<s>
Operating	O
systems	O
made	O
for	O
computers	O
with	O
blinkenlights	O
,	O
for	O
example	O
,	O
RSTS/E	B-Operating_System
and	O
RSX-11	B-Application
,	O
would	O
frequently	O
have	O
an	O
idle	B-Algorithm
task	I-Algorithm
blink	O
the	O
panel	O
lights	O
in	O
some	O
recognizable	O
fashion	O
.	O
</s>
<s>
The	O
Master	B-Application
Control	I-Application
Program	I-Application
for	O
the	O
Burroughs	O
Corporation	O
B6700	B-Device
mainframe	I-Device
would	O
display	O
a	O
large	O
block-letter	O
"	O
B	O
"	O
when	O
the	O
system	O
was	O
idle	B-Algorithm
.	O
</s>
<s>
Switches	O
and	O
lights	O
required	O
little	O
additional	O
logic	O
circuitry	O
and	O
usually	O
no	O
software	O
support	O
,	O
important	O
when	O
logic	O
hardware	B-Architecture
components	O
were	O
costly	O
and	O
software	O
often	O
limited	O
.	O
</s>
<s>
This	O
baroque	O
style	O
of	O
front	B-Device
panels	I-Device
began	O
to	O
die	O
out	O
in	O
1964	O
when	O
Seymour	O
Cray	O
designed	O
his	O
CDC	B-Device
6600	I-Device
supercomputer	I-Device
with	O
a	O
very	O
simple	O
and	O
elegant	O
display	O
console	O
containing	O
only	O
2	O
CRT	B-Device
displays	I-Device
and	O
a	O
keyboard	O
,	O
replacing	O
all	O
the	O
hundreds	O
of	O
switches	O
,	O
buttons	O
,	O
and	O
blinking	O
lights	O
.	O
</s>
<s>
Early	O
microcomputers	B-Architecture
such	O
as	O
the	O
1975	O
Altair	B-Architecture
8800	I-Architecture
also	O
relied	O
on	O
front	B-Device
panels	I-Device
,	O
but	O
since	O
the	O
introduction	O
of	O
the	O
Apple	B-Device
II	I-Device
,	O
TRS-80	B-Device
,	O
and	O
Commodore	B-Device
PET	I-Device
during	O
the	O
home	O
computer	O
boom	O
of	O
1977	O
,	O
the	O
vast	O
majority	O
of	O
microcomputers	B-Architecture
came	O
with	O
keyboards	O
and	O
connections	O
for	O
TV	O
screens	O
or	O
other	O
monitors	O
.	O
</s>
<s>
An	O
operator	O
would	O
use	O
the	O
front	B-Device
panel	I-Device
to	O
bootstrap	B-Operating_System
the	O
computer	O
,	O
to	O
debug	B-Device
running	O
programs	O
,	O
and	O
to	O
find	O
hardware	B-Architecture
faults	O
.	O
</s>
<s>
These	O
were	O
typically	O
used	O
for	O
booting	B-Operating_System
and	O
debugging	O
.	O
</s>
<s>
Typically	O
,	O
the	O
operator	O
would	O
have	O
a	O
written	O
procedure	O
containing	O
a	O
short	O
series	O
of	O
bootstrap	B-Operating_System
instructions	O
to	O
be	O
hand-entered	O
using	O
,	O
e.g.	O
,	O
dials	O
,	O
keyboard	O
,	O
toggle	O
switches	O
.	O
</s>
<s>
For	O
easier	O
entry	O
and	O
readout	O
,	O
on	O
some	O
computers	O
(	O
such	O
as	O
the	O
DEC	B-Device
PDP-8	I-Device
or	O
MITS	B-Architecture
Altair	I-Architecture
8800	I-Architecture
)	O
binary	O
digits	O
were	O
grouped	O
into	O
threes	O
or	O
fours	O
on	O
the	O
front	B-Device
panel	I-Device
,	O
with	O
each	O
group	O
of	O
lights	O
or	O
switches	O
representing	O
a	O
single	O
octal	O
(	O
between	O
0	O
and	O
7	O
)	O
or	O
hexadecimal	O
(	O
between	O
0	O
and	O
F	O
)	O
digit	O
.	O
</s>
<s>
Some	O
decimal	O
computers	O
,	O
e.g.	O
,	O
IBM	B-Device
1620	I-Device
,	O
used	O
binary-coded	O
decimal	O
for	O
memory	B-General_Concept
addresses	O
.	O
</s>
<s>
After	O
entering	O
several	O
of	O
these	O
instructions	O
(	O
some	O
computers	O
had	O
a	O
deposit	O
next	O
button	O
,	O
which	O
would	O
deposit	O
subsequent	O
values	O
in	O
subsequent	O
addresses	O
,	O
relieving	O
the	O
operator	O
of	O
needing	O
to	O
enter	O
subsequent	O
addresses	O
)	O
,	O
the	O
operator	O
would	O
then	O
set	O
the	O
starting	O
address	O
of	O
the	O
bootstrap	B-Operating_System
program	I-Operating_System
and	O
press	O
the	O
run	O
switch	O
to	O
begin	O
the	O
execution	O
of	O
the	O
program	O
.	O
</s>
<s>
The	O
bootstrap	B-Operating_System
program	I-Operating_System
usually	O
read	O
a	O
somewhat	O
longer	O
program	O
from	O
punched	O
paper-tape	O
,	O
punched	O
cards	O
,	O
magnetic	O
tape	O
,	O
drum	O
or	O
disk	O
which	O
in	O
turn	O
would	O
load	O
the	O
operating	O
system	O
from	O
disk	O
.	O
</s>
<s>
Some	O
machines	O
accelerated	O
the	O
bootstrap	B-Operating_System
process	O
by	O
allowing	O
the	O
operator	O
to	O
set	O
the	O
controls	O
to	O
contain	O
one	O
or	O
two	O
machine	B-Language
language	I-Language
instructions	O
and	O
then	O
directly	O
executing	O
those	O
instructions	O
.	O
</s>
<s>
Other	O
machines	O
allowed	O
I/O	O
devices	O
to	O
be	O
explicitly	O
commanded	O
from	O
the	O
front	B-Device
panel	I-Device
(	O
for	O
example	O
,	O
"	O
Read-In	O
Preset	O
"	O
on	O
the	O
PDP-10	B-Device
or	O
the	O
accessing	O
of	O
memory-mapped	B-Architecture
I/O	I-Architecture
devices	O
on	O
a	O
PDP-11	B-Device
)	O
.	O
</s>
<s>
Some	O
machines	O
also	O
contained	O
various	O
bootstrap	B-Operating_System
programs	I-Operating_System
in	O
ROM	B-Device
and	O
all	O
that	O
was	O
required	O
to	O
boot	B-Operating_System
the	O
system	O
was	O
to	O
start	O
it	O
executing	O
at	O
the	O
address	O
of	O
the	O
correct	O
ROM	B-Device
program	O
.	O
</s>
<s>
Front	B-Device
panels	I-Device
were	O
often	O
used	O
to	O
debug	B-Device
programs	O
when	O
operating	O
support	O
was	O
limited	O
and	O
most	O
programs	O
were	O
run	O
in	O
stand-alone	O
mode	O
.	O
</s>
<s>
The	O
contents	O
of	O
registers	B-General_Concept
and	O
memory	B-General_Concept
would	O
be	O
displayed	O
in	O
the	O
front-panel	O
lights	O
.	O
</s>
<s>
The	O
programmer	O
could	O
read	O
and	O
alter	O
register	O
contents	O
,	O
change	O
program	O
instructions	O
or	O
data	O
in	O
memory	B-General_Concept
or	O
force	O
a	O
branch	O
to	O
another	O
section	O
of	O
code	O
.	O
</s>
<s>
Programs	O
called	O
debuggers	B-Application
were	O
written	O
which	O
provided	O
the	O
programmer	O
with	O
the	O
equivalent	O
of	O
the	O
front-panel	O
functions	O
without	O
requiring	O
the	O
entire	O
machine	O
.	O
</s>
<s>
Front	B-Device
panels	I-Device
in	O
the	O
late	O
1960s	O
and	O
early	O
1970s	O
were	O
quite	O
brightly	O
colored	O
.	O
</s>
<s>
When	O
bootstrap	B-Operating_System
ROMs	O
enabled	O
computers	O
to	O
start	O
themselves	O
without	O
operator	O
intervention	O
in	O
the	O
late	O
1970s	O
and	O
early	O
1980s	O
,	O
most	O
computers	O
were	O
built	O
without	O
a	O
front	O
switch	O
panel	O
.	O
</s>
<s>
High-powered	O
calculators	O
,	O
such	O
as	O
the	O
HP	B-Device
9830	I-Device
based	O
on	O
ROM	B-Device
,	O
were	O
among	O
the	O
first	O
computers	O
to	O
do	O
away	O
with	O
front	B-Device
panels	I-Device
,	O
and	O
operators	O
.	O
</s>
<s>
The	O
following	O
procedure	O
would	O
bootstrap	B-Operating_System
a	O
PDP-8	B-Device
system	O
from	O
an	O
RK05	B-Device
moving-head	O
magnetic	B-Architecture
disk	I-Architecture
:	O
</s>
<s>
Ensure	O
that	O
the	O
machine	O
is	O
halted	O
by	O
lowering	O
and	O
raising	O
the	O
Halt	O
switch	O
;	O
the	O
front	B-Device
panel	I-Device
"	O
RUN	O
"	O
light	O
should	O
then	O
be	O
off	O
.	O
</s>
<s>
This	O
process	O
works	O
by	O
depositing	O
a	O
simple	O
,	O
two-instruction	O
program	O
in	O
memory	B-General_Concept
and	O
executing	O
it	O
.	O
</s>
<s>
The	O
first	O
instruction	O
commands	O
the	O
disk	O
controller	O
to	O
begin	O
reading	O
the	O
disk	O
from	O
the	O
current	O
disk	O
address	O
into	O
the	O
current	O
memory	B-General_Concept
address	O
.	O
</s>
<s>
When	O
"	O
Clear	O
"	O
is	O
pressed	O
,	O
the	O
disk	O
controller	O
's	O
current	O
disk	O
address	O
is	O
set	O
to	O
sector	O
0	O
and	O
its	O
current	O
memory	B-General_Concept
address	O
is	O
set	O
to	O
memory	B-General_Concept
location	O
0000	O
.	O
</s>
<s>
When	O
the	O
read	O
is	O
commanded	O
,	O
the	O
program	O
stored	O
in	O
disk	O
sector	O
0	O
overlays	O
the	O
bootstrap	B-Operating_System
program	I-Operating_System
and	O
,	O
once	O
the	O
JMP	O
instruction	O
is	O
overlaid	O
,	O
the	O
disk	O
program	O
takes	O
control	O
of	O
the	O
machine	O
.	O
</s>
