Format of dictionary (LETT) array
=================================

An item of length n bytes is stored as:
   1 byte containing n
   n bytes containing the bytes of the name

Format of dictionary hash table (WORD)
======================================

This is an open hash table. Each item is an integer containing the index
in LETT of the actual string describing the identifier

Format of the main list (ASL)
=============================

This is a record array of length [asl+1].
Initially, the top 240 entries (from 'aslcurbtm' upwards) are used as the asl
for the push/pop operations. If 'morespace' is called, 'aslcurbtm' is moved
down by some computed amount, and the new area thus created is linked into the
asl as a new set of formatted (linked) records.

The lower part of the asl is used as a constant list; this extends to
'constlimit' (8 bytes below the current asl bottom), with the free pointer
in 'constptr'.


Values for ptype
================

0  - nothing
1  - in main program block