Rockwell Automation 1771-DB BASIC MODULE - Manual (Page 111)

9 Chapter
9 -1
Expressions, Variables and Operators
This chapter describes: On page:
expressions 9 -1
relational expressions 9 -1
constants 9 -1
variables 9 -2
order of operations 9 -3
arithmetic operators 9 -5
bitwise operators 9 -7
relational operators 9 -9
trigonometric operators 9 -10
functional operators 9 -11
logarithmic operators 9 -13
string operators 9 -14
special function operators 9 -17
what’s next? 9 -20
An expression is a logical mathematical expression that uses operators,
constants, and variables to produce a result. Expressions can be simple or
complex.
simple expression: A+B–C or 10*X/20
complex expression: 12*(SIN(A)*SIN(A)+COS(A))*(COS(A)/2)
A stand alone variable or constant is also considered an expression.
Relational expressions involve the operators EQUAL (=), NOT EQUAL
(<>), GREATER THAN OR EQUAL TO (>=), and LESS THAN OR
EQUAL TO (<=). You use them in control statements to test a condition
(ex. IF A<100 THEN...). Relational expressions always require two
operands. See relational operators on page 9 -9 for more information.
A constant is a real number that ranges from
±
1E –127 to
±
.9999999 9E +127 .
A constant can be an integer.
What’s in This Chapter?
Expressions
Relational Expressions
Constants