This file is part of The Didactic PDP-8 Assembler
    Copyright (C) 2002-5 Toby Thain, toby@telegraphics.com.au

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by  
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License  
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

README
------

This program is intended to be a basic example of an assembler for a simple
architecture, written with the aid of flex and bison. Being small, the
assembler may lend itself to learning, extension and modification by
interested parties. While I do not own a PDP-8 (more's the pity), this
architecture was chosen partly for its similarity to another DeCastro design,
the DG Nova 3. The project was mainly inspired by my friend Emil Sarlija 
( http://www.chookfest.net/ ) who owns two Nova 3 computers and needed an assembler.

PDP-8

The PDP-8 assembler ("p8a") input syntax is compatible with the assembler 
described in the "PAL III Symbolic Assembler PDP-8 Programming Manual,"
Digital Equipment Corporation publication DEC-08-ASAC-D
(see http://www.pdp8.net/pdp8cgi/query_docs/view.pl?id=31 
or http://highgate.comm.sfu.ca/~djg/htdocs/cgi-bin/tifftopdf.cgi/dec-08-asac-d.pdf?loc=newstuff
or http://www.pdp8.net/pdp8cgi/query_docs/tifftopdf.pl/pdp8docs/dec-08-asac-d.pdf )

Binary object output is in RIM or BIN format. Some of the output routines
are based on parts of Douglas Jones' PDP-8 assembler
( ftp://ftp.cs.uiowa.edu/pub/jones/pdp8/pal.c.Z ).

The "verbose" mode (-v) includes a disassembler with a "diagrammatic" output
format designed to show each instruction's physical layout (in particular
the microcoded instructions).

DG NOVA

An assembler for DG Nova architecture is also included. This follows the
User's Manual (Programmer's Reference) for the DG Nova range of computers.
The instruction set, addressing modes and syntax are complete, but
the Nova native object file format (RB) is only partially implemented.
(An RB format file dump utility, dumprb, is included in the Nova directory.)

Nova bootstrap format is also supported with the -b flag;
this is program of up to 191 words assembled at an absolute origin of 0100
(see Nova Programmer's Reference, page VI-7, for more details).

Notes on building

This program has been built and tested under NetBSD 1.5/SPARC, 
Linux/Alpha (Debian 2.2), OS X 10.2,3,4 (PowerPC G4), NEXTSTEP 3.3/HPPA.

1. GNU make is required 
2. flex ( http://www.gnu.org/directory/flex.html ) is required, 
as the lexical analysers use features not available in traditional UNIX lex.

Please contact the author with any bug reports, suggestions or comments. 
The latest version is always available from the Subversion repository at
http://www.telegraphics.com.au/svn/dpa/trunk/