Appendix B - Summary of 1620 Operating Principles
Typewriter Input
Th
e typewriter IS
part
of the
16
20 console
and
is used
for both
input
and
output.
Input
Th
e typ
ew
riter is used to e
nt
er
both
data
and
instruc-
tions direc
tl
y into cor storage. Press
in
g the console
insert key unlocks the keyboard and permits
data
to be
e
nt
red into core storage starting
at
loca
ti
on 00000.
Each
de
pr
ession of a typ
ew
riter key enters the char-
acter into core storage one location
hi
gher than the
previous character.
As
many as 100 characters can
be
e
nt
ered from the typ
ew
rite
r.
After the 100th character
is
e
nt
ered, an automatic release is initiated and the
machine returns to manual mod
e.
Figure
1.
IBM
1620
I/O
Typewriter
When
I
ss
than 100 characters
ar
e e
nt
ered, entry of
the last desired c
haract
er should be followed
by
pre
ss-
ing the console release
and
s
tart
keys, or by
pr
essing
th R-S key on the typewriter keyboard.
Th
e
R-S
key
combin
es
the release
and
start
functions of the console
keys.
Th
e R-S symbol
is
typed
as
a permane
nt
record
that the R-S key has
be
en used.
Programmed selection of the typewriter unlocks the
keyboard and leaves the
computer
in automatic mode
for manual entry of
dat
a on the typewrite
r.
Data
e
ntr
y
starts
at
the addressed location (P
address)
of the in-
struction
and
e
nt
ers core storage
at
success
iv
ely
hi
gher-
order positions until the release key is depressed.
If
a record mark is required in core storage following
the last character e
nt
ered, the reco
rd
mark key on the
typewriter
mll
st be pressed befor press
in
g the release
k
ey
on the consol
e.
Appendix
B 83
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