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the even-digit planes. The 4 core is on in the odd-
digit plane. Thus
MBR-E
and
MBR-O
contain 64.
Because all 12 core planes are affected, any single-
core storage address affects two adjacent storage posi-
tions: one with an odd-numbered address and one
with an even-numbered address. Even-numbered ad-
dresses affect the next higher position. If the digit
at address 00500 (even) is addressed and program-
med to be read from core storage, the digit at address
00501 is also read. Odd-numbered addresses affect
the next lower position. Address 00501 (odd) also
affects address 00500. The selection of the digit to
be used is determined by the operation to be per-
formed. The digit actually addressed is moved to the
I-digit Memory Data Register.
Sequential Core Storage Addressing
Core storage positions are addressed sequentially from
00000 to the highest-numbered address of the core
storage positions installed-19999, 39999, or 59999.
Character transfer to, from, and within core storage
embodies the c'wrap around" principle, i.e., the
highest-numbered address is followed by the lowest-
numbered address when incrementing and the lowest-
numbered address is followed by the highest-num-
bered address when decrementing. Thus, assuming a
20,000-position core storage capacity, the increment-
ing sequence is 19998, 19999, 00000, 00001, etc.; and
the decrementing sequence is 00001, 00000, 19999,
19998, etc.
Character Representation
The 1620 can be programmed to read and write
numeric and alphameric data. The input! output in-
struction (numeric or alphameric) determines wheth-
er data is read and/or written numerically or alpha-
merically.
Numerical Representation
One decimal digit is required in core storage to rep-
resent a numerical character. No alphabetic or special
characters except the record mark and numeric blank
can be represented in the numeric mode.
Alphameric Representation
Two decimal digits are required in core storage to
represent an alphameric character, i.e., an alphabetic
character, a special character, or a numeric character.
A 2-digit alphameric representation of numeric char-
acters is provided to permit reading of mixed alpha-
betic,
special
and
numeric
characters
without
changing from an alphameric to a numeric instruction.
6
Figure 3 shows the bit configuration of a <CU" if the
1620 is in the alphameric mode. The two alphameric
digits of a character must occupy adjacent core stor-
age positions, and the zone digit must occupy the
even address. This storage requirement is satisfied by
programming;
alphameric
read/write
instructions
must contain an odd-numbered P address. Figure 4
shows the zone and numeric digits that have been
assigned to represent all the alphameric characters
used in the 1620.
rr
zone Digit
,-Numerical Digit
+
r-Character
00
b
03
04
)
10
+
13
$
14
*
20
-
21
/
23
I
24
(
33
=
34
@
41
A
42
B
43
C
44
D
45
E
46
F
47
G
48
H
49
I
50
0
51
J
52
K
53
L
54
M
55
N
56
0
57
P
58
Q
59
R
62
5
63
T
64
U
65
V
66
W
67
X
68
Y
69
Z
70
0
71
1
72
2
73
3
74
4
75
5
76
6
77
7
78
8
79
9
Figure 4.
Alphameric Codes
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