For example, AL1(stuff) defines a one-byte adcon, useful mainly for small constants with relocatable values.
'Y' adcons can directly address up to 32K bytes of storage, and are not widely used since early System/360 assemblers did not support a 'Y' data type.
A J adcon is set by the linkage editor to hold the cumulative length of the External Dummy Section, and does not actually contain an address.
An absolute expression can be completely evaluated at assembly time and does not require further processing by the linkage editor.
A complex relocatable expression contains terms that relate to addresses in different source modules.