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94 lines
2.9 KiB
Markdown
94 lines
2.9 KiB
Markdown
The logical [AND](AND) numerical operator compares two values in respect of their bits. If both bits at a certain position in both values are set, then that bit position is set in the result.
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## Syntax
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> result = firstvalue AND secondvalue
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## Description
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* [AND](AND) compares the bits of the firstvalue against the bits of the secondvalue, the result is stored in the result variable.
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* If both bits are on (1) then the result is on (1).
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* All other conditions return 0 (bit is off).
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* AND is often used to see if a bit is on by comparing a value to an exponent of 2.
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* Can turn off a bit by subtracting the bit on value from 255 and using that value to AND a byte value.
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The results of the bitwise logical operations, where *A* and *B* are operands, and *T* and *F* indicate that a bit is set or not set:
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| A | B | | [NOT](NOT) B | A [AND](AND) B | A [OR](OR) B | A [XOR](XOR) B | A [EQV](EQV) B | A [IMP](IMP) B |
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| - | - | - | - | - | - | - | - | - |
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| T | T | | F | T | T | F | T | T |
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| T | F | | T | F | T | T | F | F |
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| F | T | | F | F | T | T | F | T |
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| F | F | | T | F | F | F | T | T |
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**[Relational Operations](Relational-Operations) return negative one (-1, all bits set) and zero (0, no bits set) for *true* and *false*, respectively.**
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This allows relational tests to be inverted and combined using the bitwise logical operations.
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## Example(s)
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*Example 1:*
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```text
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101
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AND
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011
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-----
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001
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```
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> The 101 bit pattern equals 5 and the 011 bit pattern equals 3, it returns the bit pattern 001 which equals 1. Only the Least Significant Bits (LSB) match. So decimal values 5 AND 3 = 1.
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*Example 2:*
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```text
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11111011
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AND
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11101111
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----------
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11101011
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```
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> Both bits have to be set for the resulting bit to be set. You can use the [AND](AND) operator to get one byte of a two byte integer this way:
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> firstbyte = twobyteint AND 255
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> Since 255 is 11111111 in binary, it will represent the first byte completely when compared with AND.
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> To find the second (HI) byte's decimal value of two byte [INTEGER](INTEGER)s use: secondbyte = twobyteint \ 256
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Finding the binary bits on in an [INTEGER](INTEGER) value.
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```vb
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DO
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INPUT "Enter Integer value from -32768 to 32767 (Enter quits): ", INTvalue&
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IF INTvalue& < -32768 OR INTvalue& > 32767 OR INTval& = 0 THEN EXIT DO
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FOR exponent = 15 TO 0 STEP -1
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IF (INTvalue& AND 2 ^ exponent) THEN PRINT "1"; ELSE PRINT "0";
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NEXT
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PRINT " "
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LOOP UNTIL INTvalue& = 0 'zero entry quits
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```
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> Example output for 6055.
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```text
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0001011110100111
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```
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> *Note:* The value of 32767 sets 15 bits. -1 sets all 16 bits. Negative values will all have the highest bit set. Use [LONG](LONG) variables for input values to prevent overflow errors.
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## See Also
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* [OR](OR), [XOR](XOR), [NOT](NOT) (logical operators)
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* [AND (boolean)](AND-(boolean))
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* [Binary](Binary), [Boolean](Boolean)
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