> Don’t think TeX ever did that, that was a “simple” Pascal program.

Not exactly the entire process image, no, but essentially all of its data in a single chunk. It’s a peculiar Pascal program because it bypasses basically all of Pascal’s typing, records, etc., and instead builds its own from a set of (WEB) macros on top of a giant untyped array. Quoth Knuth in TeX: The Program §115:

> The dynamic storage requirements of TeX are handled by providing a large array mem in which consecutive blocks of words are used as nodes by the TeX routines. Pointer variables are indices into this array [...].

There are a few more areas designated for specific purposes, but at the end of the day (§1302) it works out about the way you’d expect:

  procedure store_fmt_file;
  [...] begin ⟨ If dumping is not allowed, abort 1304 ⟩
  ⟨ Create the format ident, open the format file, and inform the user that dumping has begun 1328 ⟩;
  ⟨ Dump constants for consistency check 1307 ⟩;
  ⟨ Dump the string pool 1309 ⟩;
  ⟨ Dump the dynamic memory 1311 ⟩;
  ⟨ Dump the table of equivalents 1313 ⟩;
  ⟨ Dump the font information 1320 ⟩;
  ⟨ Dump the hyphenation tables 1324 ⟩;
  ⟨ Dump a couple more things and the closing check word 1326 ⟩;
  ⟨ Close the format file 1329 ⟩;
  end;