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8
p
C E
B TS
OCTAL
CODE
GRA
IN
THE 91
B
NTRODUCTIO
TO PROGR
MI G
As previously described
,
there are sixteen registers per page:
(
+
) 0 through (
)
d
-
these registers are used for
either program steps or data storage;
(
+
)
e
through (
-1
)
f
-
these registers are used
for
data storage only.
The twenty-eight program registers
, (+
) 0 through
(+
)
d,
each
contain fourteen
locations
called 'characters
'
; each character
can contain
either,
one program step (one key strake) which
gives a maximum capacity of 392 program steps, or one digit
of a data number. Each piece of data consists of a twelve-digit
number and a two-digit exponent so that, if data is stored in
the program registers, a complete register is required
for
each
number.
The maximum program size of 392 steps is reduced
by
14
steps
for
each program register used for data storage.
Data and program steps cannot both be stored in any one regis-
ter at the same time.
Each
'
~haracter'
has a unique
three-part
address;
the three
parts are (always in
this
order):
1)
the
sign of
the
page
<
+
or
-
),
2)
the
register designation (0 through
d),
3)
the
character designation (0 through
d
).
Thus, the third character
in
register
c
on
the
(-
) page is
ad-
dressed as
'(-
)
c2';
'(-
)2
c
'
is
the
address of character
c
in
the third
register
on the
(-
) page;
'(+
)2
c'
is
the
address of character
c
in the third
register on
the
(
+
)
page.
Each character
has a
depth
of
six
locations; the locations are
known
as 'bits'.
lt
is
these
six 'bits'
which
contain
in a coded
form, either one program
step
or, alternatively, one digit of a
data number.
The code for each key is shown
in
the Appendix at the back of
this manual and also on the pull-out card located at the lower
front of the calculator. The code is in
'octal'
form (based on 8
instead of the normal
10
so that there are no B's or 9's); each
key of the calculator is represented by a two-digit number and
can, therefore, be used in a program. STEP PRGM (octal 51)
is not usable as a program step.
Any one of the two-digit in struction codes can be
~to_red
in the
six 'bits' or each character (this is not a contrad1ct1on of the
earlier statement, that only one data digit can be stored per
character, as each data digit requires a two-digit Gode-number).
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