65
• Logical operation
Logical operation
The task of giving YES
or
ON results, by judgment, are not few
in
computers. Here
let
us
consider some logical expressions used to judge some conditions. The logical
operators
NOT, AND,
OR
and
XOR
are used
in
logical expressions.
CD
X AND Y (logical product = and)
AND means X moreover Y
XY
X and Y
1 1 1
1
0 0
0
1 0
0 0 0
® NOT X (negation = not)
Means that it
is
not X
NOT
X
o
® X
OR
Y (logical addition = inclusive or)
OR
means either X
or
Y
XY
XORY
1 1
1
1
0
1
0
1 1
0
0 0
@ X
XOR
Y (Exclusive logical addition =
exclusive or)
Means X and
Y are not equal
XY
XXORY
1 1
0
1 0
1
0 1
1
0 0
0
The logical operation
is
usually used in
IF
-
THEN
- ELSE command, explained
before. For instance, it
is
used as follows:
•
IF
-30<X
AND
Y>20
THEN
120
ELSE
100
(The meaning above
is:
if the X value
is
-30<X
moreover
Y>29
go to line number
120,
if not jump to line
100)
•
IF
-30<X
OR
Y>20
THEN
10
ELSE
100
(The meaning above
is:
if the X value
is
-30<X
or
Y>20
to to line number 120, if
not jump to line
100).
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