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3 HANDLING OF CHARACTERS AND NUMERIC VALUES IN ST PROGRAMS
(2) Character types
The characters used in ST programs can be classified as indicated below.
Classification Description
Example
Label name
Character string defined as
desired by the user.
It includes a function block
name, array name, structure
name, etc.
Switch_A
Constant
Value written directly to a
program.
(Integer, real number,
character string, etc.)
123, "abc"
Comment
Commentary statement that
is not the processing target
of control in a program.
(* Turns ON *)
Data type
name
Word that represents a data
type.
BOOL, DWORD
Control
syntax
Word whose meaning has
been defined grammatically
for use as a control syntax.
IF, CASE, WHILE, RETURN
Device
name
Data name for MELSEC
PLC
X, Y, M, ZR
Reserved
word
Function
name
MELSEC function/IEC
function name already
defined.
OUT_M
REAL_TO_STR_E
Operator
Character code whose
meaning has been defined
for an expression or
assignment statement.
+ - < > =
Delimiter
Character code whose
meaning has been defined to
clarify a program structure.
; ( )
Other symbols
Code for putting a layout in
order.
Space
Line feed code, TAB
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