( )
Remarks
Parentheses are used in ST
"Structured text"
A high-level language that is block structured and syntactically resembles Pascal and IL"Instruction list"
This is a low-level language and resembles assembly language for changing the default evaluation order of
various operations within a complex expression. For instance, the default evaluation of
"2 * 3 + 4" expression in ST language gives a result of 10 as "*"
operator has highest priority. Changing the expression as "2 * ( 3 + 4 )" gives
a result of 14. Parentheses can be nested in a complex expression.
Below is the default evaluation order for ST language operations (1rst is highest priority):
| Unary operators | - NOT |
| Multiply/Divide | * / |
| Add/Subtract | + - |
| Comparisons | < > <= >= = <> |
| Boolean And | & AND |
| Boolean Or | OR |
| Exclusive OR | XOR |
In IL language, the default order is the sequence of instructions. Each new instruction modifies the current result sequentially. In IL language, the opening parenthesis "(" is written between the instruction and its operand. The closing parenthesis ")" must be written alone as an instruction without operand.
ST Language
Q := (IN1 + (IN2 / IN 3)) * IN4;
FBD Language
Not available
FFLD Language
Not available
IL Language
Op1: FFLD( IN1
ADD( IN2
MUL IN3
)
SUB IN4
)
ST Q (* Q is: (IN1 + (IN2 * IN3) - IN4) *)
See also
