Number attributes for SET symbols

The number attribute (N') can be applied to SETx variables to determine the highest subscript value of a SET symbol array to which a value has been assigned in a SETx instruction. For example, if the only occurrences of the definitions of the SETA symbol &A are:
Name      Operation      Operand

&A(1)     SETA           0
&A(2)     SETA           0
&A(3)     SETA           &A(2)
&A(5)     SETA           5
&A(10)    SETA           0
then N'&A is 10.

The number attribute is zero for a SET symbol that has been defined but not assigned any value, regardless of whether it is subscripted or not. The number attribute is always 1 for a SET symbol that is not subscripted and when the SET symbol has been assigned a value.

The number attribute also applies to the operands of macro instructions.