A pointer stores the memory address of objects, such as variables or function block instances, at runtime.

Syntax of the pointer declaration:

‎<pointer name>: POINTER TO <data type> | <data unit type> | <function block name> ;‎

FUNCTION_BLOCK FB_Point
VAR
    piNumber: POINTER TO INT;
    iNumber1: INT := 5;
    iNumber2: INT;
END_VAR
piNumber := ADR(iNumber1); // piNumber is assigned to address of iNumber1
iNumber2 := piNumber^; // value 5 of iNumber1 is assigned to variable iNumber2 by dereferencing of pointer piNumber

Dereferencing a pointer means obtaining the value to which the pointer points. A pointer is dereferenced by appending the content operator ‎^‎ to the pointer identifier (example:, ‎piNumber^‎ in the example above). To assign the address of an object to a pointer, the address operator ‎ADR‎ is applied to the object: ‎ADR(iNumber1)‎.

In online mode, you can use ⮫ “Command: Go to Reference ” to jump from a pointer to the declaration location of the referenced variable.

NOTICE

When a pointer points to an I/O input, write access applies. When the code is generated, this leads to the compiler warning “'<pointer name>' is not a valid assignment target”. Example: ‎pwInput := ADR(wInput);‎

If you require a construct of this kind, you have to first copy the input value (‎wInput‎) to a variable with write access.