Fixed-Point Arithmetic Instructions - IBM 7090 Instruction-Reference

Accumulator Right Shift
ARS +0771 (I, L ••• ) Figure 5.3-11
This instruction causes the contents of AC (Q-35) to be shifted right the number of
places indicated by the address. Bits shifted away from Q are replaced by zeros; bits
shifted past position (35) are lost. ARS is similar to ALS except for direction of the
shifting.
Long Right Shift LRS +0765 (I, L ... ) Figure 5.3-12
The contents of the MQ and AC (except the sign positions) are shifted right the
number of places indicated by the address. The MQ sign is set to agree with the AC
sign. Bits shifted away from Q are replaced by zeros and shifted past AC(35) enter
MQ(1). Bits shifted past MQ(35) are lost.
Logical Right Shift LGR -0765 (I, L ... ) Figure 5. 3-12
This instruction shifts the contents of the AC(Q-35) and MQ(S-35) right the number
of places designated by the address. Bits shifted out of AC(35) are entered into MQ(S)
and from MQ(S) to MQ(1). Bits shifted past MQ(35) are lost. The operation of LGR is
the same as LRS except for the handling of the MQ sign.
Rotate MQ Left
RQL -0773 (I, L •.. ) Figure 5.3-13
This instruction shifts the contents of the MQ, including the sign, left the number
of places designated by the address. Bits shifted out of MQ(l) enter the sign position
and from the sign position enter MQ(35).
5.3.03 Fixed-Point Arithmetic Instructions
Fixed-point arithmetic instructions are the basic calculating instructions. Addition
is the foundation of all of these instructions, and parts of the ADD instruction will be
found in all instructions. All arithmetic instructions use the accumulator.
Clear and Add CLA +0500 (I, E) Figure 5.3-14
The instruction clears the AC (S, Q-35) and loads positions (S, 1-35) with the con-
tents of the storage location indicated by the address. The word that is to be put into
the AC is brought from core storage to the SR during the E cycle. In the I cycle of the
next instruction, positions (1-35) are gated from the SR through the AD to the AC. The
sign position is gated directly from the SR to the AC.
Clear and Subtract CLS +0502 (I, E)
Figure 5.3-14
This instruction replaces the contents of the AC with the word from the core storage
location indicated by the address. The sign of the word is reversed. Execution of this
instruction is the same as the CLA except that the sign of the word is inverted during
the E cycle after the word has entered the SR.
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