🚀 go-pugleaf

> Odd tags indicate that the contents of the memory may not be accessed
> as normal data.  They do not distinguish whether a word is read-only;
> a separate bit in the descriptor indicates read-only status.  And
> even a read-only word can be written to with the overwrite instruction.
> Odd tags are used for a variety of purposes - e.g., the start and
> end of arrays in memory, data descriptors, instruction words, IRWs, PCWs.
> Attempting to access an odd tagged word as data for either reading or
> writing causes a hardware interrupt.

An IRW is an Indirect Reference Word, or a pointer in the general sense.
These tend to be used quite often.  For example, when passing a parameter
by reference.  The target of a store operation can be a data word (tag zero)
or an IRW, or a chain of IRWs, which eventually point to a data word.  The
same goes for the target of a read (get value) operation.

A PCW is a Program Control Word.  This is a special descriptor which
describes a code segment, such as a procedure.  Since this is a stack
machine, *everything* is either a single or double stack item, or a
type of descriptor.

  =====================================================================
  = sua cuique voluptas              (everyone has his own pleasures) =
  = Randy Gellens            randy%mpa15ab@trenga.tredydev.unisys.com =
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  = Opinions are personal; facts are suspect; I speak only for myself =

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You could get a new lease on life -- if only you didn't need the
first and last month in advance.