Control Data 3100 Reference Manual page 17

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TABLE 1-2. CHARACTERISTICS OF THE 3100 COMPUTER REGISTERS
REGISTER
FUNCTION
BIT
MODULUS
COMPLEMENT ARITHMETIC
RESULT
DESIGNATION CAPACITY NOTATION PROPERTIES
Main
A Arithmetic
24
224_1
one's additive signed*
register
Auxiliary
Q Arithmetic 24
224_1
one's additive signed*
register
Program
i
F** Control
24
224_1
*** ***
***
register
Communica-
C** tions 24
224_1
register
.l!'.l!'.l!'.l!'
Program
p
Address 15
2 15 _1
register
8 1 , B2, B3
Index
15
2 15 _1
one's
additive
unsigned
registers
Storage
S Address 13
213_1
register
Storage
28
Z
Data
(includes 4
224_1
register parity bits)
****
Arithmetic
X Transfer
24
224_1
register
EU and EL
EUpper and
ELower octal 48
2 48 _1
one's additive signed*
register
ED
53 (include
ED
(BCD) sign and
±
10 13
absolute additive signed
register overflow digit)
0
Field Length
4
24_1
one's
~.l!'~~
register
Since the A,
Q,
and EUEL register contents are all treated as signed quantities, the capacity of these registers is limited to the following values:
A::; 2 23 _1; Q::; 2 23 _1; EUEL::;: 24L 1. When the arithmetic result in A, Q,
or EUEL is zero, it is always represented by positive zero.
Dual purpose register.
Only the lower 15 or 17 bits of F are modified depending on whether word or character addressing is being used. The results are unsigned.
Information not applicable.