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76 lines
No EOL
2.5 KiB
Text
76 lines
No EOL
2.5 KiB
Text
The logical [[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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{{PageSyntax}}
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:{{Parameter|result}} = {{Parameter|firstvalue}} AND {{Parameter|secondvalue}}
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{{PageDescription}}
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* [[AND]] compares the bits of the {{Parameter|firstvalue}} against the bits of the {{Parameter|secondvalue}}, the result is stored in the {{Parameter|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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{{Template:LogicalTruthTable}}
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{{PageExamples}}
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''Example 1:''
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{{WhiteStart}}
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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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{{WhiteEnd}}
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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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{{WhiteStart}}
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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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{{WhiteEnd}}
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:Both bits have to be set for the resulting bit to be set. You can use the [[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]]s use: secondbyte = twobyteint \ 256
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''Example 3:'' Finding the binary bits on in an [[INTEGER]] value.
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{{CodeStart}}
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DO
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{{Cl|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 {{Cl|EXIT DO}}
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{{Cl|FOR...NEXT|FOR}} exponent = 15 {{Cl|TO}} 0 {{Cl|STEP}} -1
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{{Cl|IF...THEN|IF}} (INTvalue& {{Cl|AND}} 2 ^ exponent) {{Cl|THEN}} {{Cl|PRINT}} "1"; {{Cl|ELSE}} {{Cl|PRINT}} "0";
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{{Cl|NEXT}}
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PRINT " "
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LOOP UNTIL INTvalue& = 0 'zero entry quits
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{{CodeEnd}}
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:Example output for 6055.
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{{OutputStart}}
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0001011110100111
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{{OutputEnd}}
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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]] variables for input values to prevent overflow errors.
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{{PageSeeAlso}}
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* [[OR]], [[XOR]], [[NOT]] {{text|(logical operators)}}
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* [[AND (boolean)]]
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* [[Binary]], [[Boolean]]
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{{PageNavigation}} |