A new PDP-8 project, new stuff to learn

It's been over a week since my last post.  I've been pretty busy at work, with an important deadline looming, but I have to admit I've sort of been taking a break from retrocomputing for a few days.  But as I mentioned in my last post wrapping up the Retrochallenge, I planned to continue working with the PDP-8.  So here I am back at it, with a new project.

I've had a lot of ideas about what to do next, but what I've finally settled on is that I'd like to write a cross-assembler, something that will generate PDP-8 machine code in a BIN file that can be read by the paper tape reader in simh.

But this is a bit of a long-term goal, not an immediate one.  The one downside to my Retrochallenge project, as I mentioned in my previous post, is that learning Fortran shielded me from many of the lower level details of the PDP-8.  So I have to learn that, starting with the PAL8 assembly language itself.  So my next few posts will almost certainly be about what I've learned and how to write code in PAL8 assembly language.

Toward that end, I've started reading the "Introduction to Programming", put out by DEC in 1969.  It's a gentler introduction to PDP-8 assembly language than the OS/8 Handbook that I've been relying on so far.  It seems to take a lot less for granted in terms of knowledge on the part of the reader, and it does a much better job of explaining things.  This is both good and bad, of course.  For example, the first chapter covers numbering systems such as binary and octal (the standard for PDP-8 code), how to perform arithmetic operations on such numbers, etc.  Being an experienced programmer, though, this was mostly just review, so I actually ended up skipping large chunks of this.  But the second chapter starts to get into the meat of the topic, so I'm looking forward to making my way through that.

Just a quick note before going further: My experience with assembly is completely limited to microcomputers, and even then a small set.  Although I've done some x86 assembler in the past, it's been quite some time, and now its really 6502 assembly that I'm most familiar with.  So naturally as I'm working my way through PDP-8's assembly language, I can't help but compare it to the 6502, and I'm sure that will come out in my posts.  If you're not familiar with the 6502 and its assembly language idioms, then I apologize.  I can only hope that this will not prove to be too much of an obstacle.