A high level language might provide dictionary type objects.
These are sets of key and value pairs
with an arbitrary number of members.
As pairs are added, the size of the dictionary increases.
Except for constant dictionaries,
the size of a dictionary is not known beforehand.
For various applications one might be able to give an upper
limit for the size of some dictionary,
but for other applications this might be impossible.
For the latter case,
dictionaries as they are implemented with PostScript
are imperfect, as the PostScript operator to create
a new dictionary always needs to be given the maximum size
of the dictionary.
While there are PostScript implementations that ignore the
maximum value, there are others that do not,
so extra effort is mandatory where portability is a must.