The type subfield and the nominal value must always be specified
unless the duplication factor is zero. If the duplication factor
is zero, only the type must be specified.
The duplication factor, type extension, program type, and modifier
subfields are optional.
When multiple operands are specified, they can be of different
types.
When multiple nominal values are specified in the sixth subfield,
they must be separated by commas and be of the same type. Multiple
nominal values are not allowed for character or graphic constants,
because a comma is part of the nominal value of the constant; it is
not possible to specify multiple nominal values.
The descriptive subfields, apart from the program type, apply
to all the nominal values. The program type applies to only the symbol
naming the DC instruction, if a symbol was present. Separate constants
are generated for each separate operand and nominal value specified.