IBM 1620 1 Manual page 19

Add Immediate (AM-ll)
Description. The description is the same as that
for Add (A-21) except that the data in the
Q
part
of the instruction is used as the Q data. For example,
if the Op core were 11 in Figure 12, the
Q
data would
be 09400 and the result would be 12 (00
+
12). The
three high-order positions of the Q data (094) are
not used because the P-data flag bit (above the one
in 12) stops the add operation. The Arithmetic Check
i~dicator
is turned on because the
Q
data field
(09400) exceed the two digits of data (12) contained
in the field defined by the P address (00500).
Execution Time. Same as Add.
Subtract (5-22)
Description. The data in the field at the
Q
address is subtracted from the data in the field at the
P address and the difference replaces the data in the
field at the
P
address. The data in the field at the
Q
address remains unchanged.
The data in the field at the Q address is comple-
mented if it has the same sign as the data in the
field at the P address.
A zero result retains the sign of the field at the
P address. The sign of a result, other than zero, is
determined by algebraic analysis of the P and Q
fields. High-order zeros are supplied if the number
of significant digits in the Q field is less than the
number of significant digits in the initial field at the
P address.
I
Address of
I
Address of
I
Op Code
r----
Multiplicand •• Multiplier
----1
Multiplicand Value
=
12
Multiplier Value
=
02
Product Value
=
0024
Figure 13. Multiply Instruction - Data Flow
The
H/P
indicator is on it the difference is positive
and not zero; the
E/Z
indicator is on if the difference
is zero. Neither indicator is on if the difference is
negative.
Execution Time. Execution time is computed by
using the Add instruction formula. Recomplement
time is added to basic time when the signs of the
fields at the Q and P addresses are the same initially
and the absolute numeric value of the field at the
Q
address is greater than the absolute numeric value
of the field at the P address.
Subtract Immediate (SM-12)
Description. The description is the same as for
Subtract (S-22) except that the digits in the
Q
part of
the instruction are used as the
Q
data.
Execution Time. Same as Subtract.
Multiply (M-23)
Description. The data in the field at the P address
is multiplied by the data in the field at the
Q
address,
and the result (product) is placed in core storage,
beginning at position 00099 and extending through
successively lower-numbered positions. The data in
the fields at the Q and P addresses is not changed by
the operation.
In Figure 13, the multiplicand (12) at 00500 is
multiplied by the multiplier (02) at 09400. The prod-
uct (0024) is developed and stored at 00096-00099.
Core Storage
Product Area
Multiply
Table
15