Anders Magnusson <ragge@ludd.luth.se> writes:
> The pdp10 can only address 36-bit words in memory in normal
> sense. There are byte instructions that can address parts of a word,
> but they require one (or two) extra words of address and also have a
> slightly different format compared to normal words.

Obi Wan error?  Small note to avoid confusion:

A PDP-10 byte pointer can address a (contigous) bit field within a
word (i.e. not crossing a word boundary).  In PDP-10 terminonlgy,
that's called a "byte".

Byte pointers can have three different formats:

* Local format: One word capable of addressing every possible bit
  field, in a word within a limited address range.

* One-word global format: One word capable of addressing a subset of
  the possible bit fields, in a word anywhere in memory.  The subset
  consists of 6-, 7-, 8-, 9-, and 18-bit fields in the most commonly
  used positions.

* Two-word global format: Two words capable of addressing every
  possible bit field, in a word anywhere in memory.