
Introduction to IEC 61131-3 programming
Appendix
21
L DDS-IEC61131 EN 2.0
6.2.2 Indication of the variable type
The indication of the variable type is optional. It can be used to indicate the variable type in the
identifier:
Variable type entry (optional) Meaning
I_ VAR_INPUT
Q_ V AR_OUTPUT
IQ_ V AR_IN_OUT
R_ VAR RET AIN
C_ VAR CONSTANT
CR_ VAR CONST ANT RETAIN
g_ VAR_GLOBAL
gR_ V AR_GLOBAL RETAIN
gC_ VAR_GLOBAL CONSTANT
gCR_ VAR_GLOBAL CONSTANT RETAIN
6.2.3 Indication of the data type
The data type entry provides information about the data type of a variable:
Data type entry Meaning
b Bool
by Byte
n Integer
w Word
dn Double Integer
dw Double Word
s String
f Real (Float)
sn Short Integer
t Time
un Unsigned Integer
udn Unsigned Double Integer
usn Unsigned Short Integer
If the variable is an array or a pointer, this will be indicated before thedatatypeentry:
Data type entry (optional) Meaning
a Array (combined type), field
p Pointer
Examples of data type entries:
aby
(ArrayofdatatypeByte)
dn
(Double Integer)
pdn
(Pointer to Double Integer)
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