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IBM 7090 - Page 61

IBM 7090
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Example
2
Signs
Unlike,
AC
Smaller
7 +
(-6)
= + 1
+0111 SR(7)
-1001
l'
s
comp
of
AC (6)
-0000
Q
carry
1 Add
one
-0001
Result
in
AC
+0001
Change
sign
Add
Magnitude
Example
3
Signs
Unlike,
AC
Greater
6 +
(-7)
=
-1
+0110 SR(6)
-1000
l'
s
comp
of
AC(7)
-1110
No Q
carry,
Result
in
AC
-0001
Comp
AC
ADM +0401 (I,
E)
Figure
5.3-15
For
this
instruction,
the
word
at
the
storage
location
indicated
by
the
address
is
to
be
considered
positive.
This
positive
word
is
added,
algebraically,
to
the
contents
of
the
AC. ADM
operates
the
same
as
ADD,
except
that
the
sign
of
the
word
is
set
posi-
tive
after
it
has
entered
the
SR.
Subtract
SUB
+0402 (1,
E)
Figure
5.3-15
This
instruction
algebraically
subtracts
the
word
at
the
storage
location
indicated
by
the
address
from
the
contents
of
the
AC.
The
execution
of
SUB
is
similar
to
ADD,
except
that
the
sign
of
the
word
in
the
SR
is
inverted.
Subtr
act
Magnitude
SBM
-0400
(I,
E)
Figure
5.3-15
For
this
instruction
the
sign
of
the
storage
word
indicated
by
the
address
is
considered
negative.
This
negative
word
is
added
algebraically
to
the
contents
of
the
AC.
The
execution
of
SBM
is
the
same
as
ADD,
except
that
the
sign
of
the
SR
word
is
forced
negative.
Add
and
Carry
Logical
Word
ACL
+0361
(I,
E)
Figure
5.3-16
This
instruction
adds
the
36-bit
logical
word
stored
at
the
location
indicated
by
the
address
to
the
contents
of
the
AC(P-35).
AC(S)
is
ignored;
AC(Q)
is
unchanged.
A
carry
out
of
AD(P)
is
added
to
position
35
in
the
adders.
The
operation
of
this
instruc-
tion
is
the
same
as
ADD,
except
for
the
handling
of
the
(S), (Q),
and
(P)
positions.
Multiply
MPY
+0200
(Min
I,
E)
Figure
5.3-17
(Max
I,
E,
12L)
This
instruction
multiplies
the
word
stored
at
the
location
indicated
by
the
address
by
the
contents
of
the
MQ.
The
35
most
significant
bits
of
the
70-bit
product
replace
the
AC(1-35),
and
the
35
least
significant
bits
replace
the
MQ(1-35).
Positions
(Q)
and
(P)
of
the
accumulator
are
cleared,
and
the
signs
of
the
AC
and
MQ
are
set
to
the
algebraic
sign
of
the
product.
00
0110
Multiplicand
(SR)
1011
Multiplier
(MQ)
0110
Partial
Product
0110
"
"
0000
"
"
0110
"
"
1000010
Product
(AC
and
MQ)
60

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