AND
The AND operator is used to perform a logical conjunction of two numbers.
Syntax
result = Number1 AND Number2
Example
The example assigns a value to Msg that depends on the value of variables A, B, and C, assuming that no variable is a Null. If A = 10, B = 8, and C = 6, both expressions evaluate True. Because both expressions are True, the AND expression is also True.
'CR6 Datalogger
Public A, B, C, Msg AS Boolean 'Declare variables.
BeginProg
A = 10: B = 8: C = 6 'Assign values.
Scan (1,Sec,3,0)
If A > B AND B > C Then 'Evaluate expressions.
Msg = True
Else
Msg = False
EndIf
NextScan
EndProg
The following program is an example of using AND to check individual bits in a Long, and using AND to mask bits.
Public SourceInteger As Long, MaskedInteger As Long
Public Bit0 As Boolean, Bit1 As Boolean
BeginProg
Scan (1,Sec,0,0)
SourceInteger = &b1100010
'Checking
individual bits with AND
Bit0 = SourceInteger AND 1 '
2^0 &b1
Bit1 = SourceInteger AND 2 '
2^1 &b1
'Using a bit mask
with AND to return a portion of the source
MaskedInteger = SourceInteger AND &b0111111
NextScan
EndProg
Remarks
The AND operator performs a bit-wise comparison of identically positioned bits in two numeric expressions and sets the corresponding bit in result according to the following truth table:
| If bit in Number1 is | And bit in Number2 is | The result is |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
Bit-wise operations are performed on integers; floating point values will first be converted before the bit-wise operation is performed. Although AND is a bit-wise operator, it is often used to test Boolean (True/False) conditions. Boolean values are implemented as Longs that are restricted to -1 (True) or 0 (False). Any non-zero number >= 1 will evaluate as true (a float value between .999 and 0 when converted to a Long is 0). Because AND is a bit-wise operation, it is possible to AND two non-zero numbers (for example, 2 and 4) and get 0. The binary representation of -1 has all bits equal 1. That is, any number AND -1 returns the original number. That is why the predefined constant True = -1.
If, and only if, both expressions evaluate True, result is True. If either expression evaluates False, then result is False. The following table illustrates how result is determined:
| If Number 1 is | AND Number2 is | The result is |
|---|---|---|
| -1 | Any number | Number2 |
| -1 | NAN Not a number. A data word indicating a measurement or processing error. Voltage overrange, SDI-12 sensor error, and undefined mathematical results can produce NAN.
|
NAN |
| 0 | Any number | 0 |
| 0 | NAN | NAN |
Expressions can be used in place of one or both of the numbers. Comparison expressions evaluate as True (-1) or False (0).