Basic instructions
8.4 Comparator operations
S7-1200 Programmable controller
254 System Manual, V4.2, 09/2016, A5E02486680-AK
Table 8- 37 Data types for the parameters
Operand2 Bit strings, integers, floating-point numbers,
timers, date and time, character strings,
ARRAY, PLC data types
Second operand
Null comparsion instructions
You can use the instructions IS_NULL and NOT_NULL to determine whether or not the input
actually points to an object or not.
For both instructions, <Operand> must have the Variant data type.
Table 8- 38 IS_NULL (Query for EQUALS ZERO pointer) and NOT_NULL (Query for EQUALS ZERO pointer) instructions
Not avail-
able
Tests whether the tag pointed to by the Variant
at Operand is null and therefore not an object.
Not avail-
able
Tests whether the tag pointed to by the Variant
at Operand is not null and therefore does point
to an object.
Table 8- 39 Data types for the parameters
Operand to evaluate for null or not null.
IS_ARRAY (Check for ARRAY)
You can use the "Check for ARRAY" instruction to query whether the Variant points to a tag
of the Array data type.
The <Operand> must have the Variant data type.
The instructions returns 1 (true) if the operand is an array.
Table 8- 40 IS_ARRAY (Check for ARRAY)
IS_ARRAY(_variant_in_) Tests whether the tag pointed to by the Variant
at Operand is an array.
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