Transcript Sec (2.4) Arithmetic / logic instruction: Logical operations:  Ex: AND 11001001OR 11001001XOR 11001001

Sec (2.4)
Arithmetic / logic instruction:
1
Logical operations:

Ex:
10011010
AND 11001001
10001000
10011010
OR 11001001
11011011
10011010
XOR 11001001
01010011
2
Mask:
Suppose we have this byte 00110011 we
need to find a mask that being given the
inverse for all digits?
 Sol.:
00110011
XOR 11111111
11001100

3
Mask:
So, note that:
1. X
AND
2. X
AND
3. X
OR
4. X
OR
5. X
XOR
6.
X
XOR
0
1
0
1
0
0
X
X
1
X
1
X
4
Rotation and shift operations:

The operation in the class of rotation and shift
operations provide a means for moving bits within a
register and are often used in solving alignment
problems. These operation are classified by the
direction of motion (right or left) and whether the
process is circular. Within these classification guidelines
are numerous variations with mixed terminology.
1.
circular shift (rotation)
logical shift
arithmetic shift
2.
3.
5
circular shift (rotation)

Ex:
Rotating the bit pattern A3 one bit to the right
6
logical shift:


another technique is to discard the bit
that falls of the edge and always fill the
hole with a 0.
Ex:
+437 / 8 = 437 / 23 it means that shift 3
bits to right
7
logical shift:
0
0
0
1
1
0
1
1
0
1
0
1
0
0
0
0
0
0
1
1
0
1
1
0
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arithmetic shift:




in either shift, care must be taken to preserve the
sign bit when using certain notational system
we often find right shifts that always fill the hole
with its original value
shifts that leave the sign bit unchanged
Ex:
+50 * 16 = 50 * 24 it means that shift 4
bits to left
9
arithmetic shift:
0
0
1
1
0
0
0
1
1
0
0
1
1
1
1
0
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