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Console Typewriter
The 1620
console
typewriter
(Figures
50
and
51
)
is
the principal
communicating
link between the opera-
tor and the
system.
Typewriter Input
The 1620 console
typewriter is
used to enter data
and instructions directly into
core
storage.
Off-line
use is not possible
because the
keyboard
(Figure
51
)
is locked
except when
entering data. Pressing
the
console
Insert
key (see Figure 50,
I
)
unlocks
the
keyboard
and
permits data to be entered into
core
storage,
starting at
location
00000.
Each depression
of
a typewriter
key
enters a character
into
core storage
one location higher than the previous
character.
As
many as 100 characters can be
entered
from the
type-
writer. After the l00th
character
is entered
,
an auto-
matic release is initiated
and
the
machine
returns to
manual
mode.
The Start key
may
then be used to
start
program operation
at
00000.
When less than 100
characters are entered, entry
of
the
last
desired
character
should
be
fol-
lowed by pressing
the
console
Release
and
Start
keys,
or
by pressing the
R-S
key
on
the typewriter
keyboard.
The
R-S
key
combines
the
release
and
start
functions of
the
console
keys. The
R-S
symbol
is typed as a
permanent record that
the
R-S
key
has
been used.
Programmed
selection of
the typewriter
(Read
Figure 50.
IBM
1620 CPU
with
I/
O Typewriter
52
Alphamerically or
Read
umerically instructions
)
unlocks the
keyboard,
leaving
the
computer in
auto-
matic mode for manual
entry
of
data
on
the
type-
writer.
Data
entry
starts
at
the
address-numbered
location
(
P
address
)
of
the
instruction
and
enters
core storage
at successively
hi gher-numbered loca-
tions
until
the Release key is
pressed
.
It should
be noted
that
the
decimal point
or
period
character in either
upper shift or
lower shift may
be
entered
only with a
Read
Alphamerically
instruc-
tion.
If
entry
is made
with
a
Read
umerically
instruction,
incorrect
data is put
into
core
storage.
If
a
record
mark is
required
in
core storage fol-
lowing
the
last character entered
, the
Record Mark
key
on
the
typewriter
must
be
pressed
before
pres-
sing
either
the
R-S
key
on
the
typewriter
or
the
Re-
lease key
on
the console ( Figure
50,
R
).
Pressing
either
key
again
locks the
keyboard
and gives
the
computer
an
end-of-inpu t/output
indication.
Typewriter Output
The
typewriter
prints
data from
core
storage when
it
is programmed
to
do
so.
When the
right-hand
margin is
reached,
the carriage returns
automatically
and
typing
continues
until a
record
mark is sensed
or until
the Release key
is pressed.
The Release key
may be
used, for
example,
"
to
terminate
a
Dump
Numerically
operation from
the
typewriter.
Parity Checking
Input data from
the
typewriter is parity-checked be-
fore
entering
core
storage.
Transmission
of
a char-
acter with incorrect
parity illuminates
the
console
Read Check light and
turns
on
the
Read Check
in-
dicator (06
).
Output data from
core storage
is parity-checked
as
it is
transmitted
to
the
typewriter. Transmission
of
a character
with
incorrect
parity
turns on the
Write
Check indicator
(07)
and
the
console
Write
Check light.
Also,
a
horizontal bar is overprinted
across
the
center of
the
character.
An
invalid
char-
acter with correct
parity
causes
a special symbol
character
(
)K
)
to print.
If
a
parity
error
ocurs,
the
input or output opera-
tion
continues until completion, and
the machine
either
stops or continues
under program
control,
de-
pending
on th
e
position of
the
console
I/O
Check
switch.
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