Rockwell Automation 57C610 Enhanced Basic Language, AutoMax - Manual (Page 36)

5Ć4
The relational operators="and < >" or > <" are used when
there is a relational or comparison expression, such as that found in
an IF"statement. The statement below tests the value of the
boolean which is the result of the string comparison. If the result is
true and the two strings are not equal (< >), the program transfers
control to line 250. The relational operator =" is used in the same
way to test strings:
20 IF C$ < > MESSAGE" THEN GOTO 250
When strings are concatenated (added) and the result is stored in a
string variable (A$ = B$ + TEXT"), the resultant length of the
computed string expression still must not exceed the maximum
length for a string (255 characters if specified in the variable
definition, 31 as a default if no size is specified). If it is longer than
the maximum, it is truncated to the maximum and loaded.
If the string expression is used in a relational expression or PRINT
statement where it is not assigned to a variable but only exists as a
temporary entity, the string expression may be as large as 132
characters.
The following are strings used as intermediate values. In both cases,
the string expression enclosed within the parentheses may be as
large as 132 characters. If it exceeds that length, it is truncated to
132 characters. This means that BASIC will allow string expressions
to be as large as 132 characters while the expression is being
computed; however, at the time it is to be assigned to a string
variable, it must be able to fit the string into the allocated variable
space (31 default, 1Ć255 if specified in the variable definition):
IF (A$ + C$) < > (B$ + TEXT") THEN 200
PRINT (HI"+ A$ + B$ + C$),N%,XYZ
5.3 Boolean Expressions
A boolean expression, just like a boolean variable, evaluates to a
true/false value. Refer to table 5.3 for the truth table. Boolean
expressions use the following boolean operators:
AND
(performs logical AND" function)
OR (performs logical OR" function)
XOR (performs logical exclusiveĆOR" function)
NOT (unary boolean operator performs a boolean
complement)
The following are boolean expressions:
OVER_TEMP@ (Simple boolean variable, TRUE or FALSE)
OVER_TEMP@ AND SHUTDOWN_READY@ (ANDs two
boolean results together)
NOT ((A@OR B@ AND C@) (complex boolean expression)