Vector Basic Interpreter Basic 80, Справочное руководство

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IF 0<200 AND F<4 TEEN 80
IF I>10 OR K<O THEN 50
IF NOT P THEN 100
Logical operators work by converting their operands to
sixteen bit, siqned, two
r
S
complement integers in the range
-32768 to +32767. (If the operands are not in this range,
an error results.) If both operands are supplied as 0 or -1,
logical operators return 0 or -1. The given operation is
performed on these integers in bitwise fashion, i.e., each
bit of the result is determined by the corresponding bits in
the two operands.
Thus, it is possible to use logical operators to test bytes
for a particular bit pattern. For instance, the AND
operator maybe used to "mask" all but one of the bits of a
status byte at a machine I/O port. The OR operator may be
used to "merge" two bytes to create a particular binary
value. Tbe following examples will help demonstrate how the
logical operators work.
63 • binary 111111 and 16 • binary
10000, so 63 AND 16 - 16
15 • binary 1111 and 14 - binary 1110,
so 15 AND 14 - 14 (binary 1110)
-1 - binary 1111111111111111 and
8 • binary 1000, so -1 AND 8 • 8
4 • binary 100 and 2 -binary 10,
so 4 OR 2 - 6 (binary 110)
10 - binary 1010, so 1010 OR 1010 •
1010 (10)
-1 • binary 1111111111111111 and
-2 • binary 1111111111111110,
so -1 OR -2 • -1. The bit
complement of sixteen zeros is
sixteen ones, which is the
two's complement representation of -1.
The two's complement of any integer
is t,hebit complement plus one.