Obsolescence Guaranteed

Introduction: Focal was a radically useful program in the early days of the PDP. Before Focal, you would load an editor, punch your program it to tape, load the assembler from another tape, load the source code, assemble, punch a executable file, then load that tape to run the program. It is even more painful than it sounds. Focal, like Basic, was revolutionary because it was Interactive. You did not have to go through that cumbersome compile cycle. You just typed in your program's instructions, ran it to see how it went, and made your changes along the way. All without any loading from or saving to tape. You could even use it as a calculator! This was huge progress in usability.

Introduction: in the hey day of the 8/I, floppy disk drives were not used. Instead, magnetic tape (DECtape) drives were the advanced storage medium. They worked like floppy disks: you can read in a particular block of data into memory, and overwrite that block. The only difference is that a lot of tape spooling was necessary to reach the desired blocks.
The PiDP can use floppy disk images just as well as DECtape images. But DECtape is the real deal.

OS/8 was a typical operating system for its time. But operating systems were not typical at all for small computers like the PDP-8, and that made OS/8 revolutionary. CP/M users will recognise quite a bit (PIP!) and MS-DOS users too will not feel too out of place. There's built-in commands, utility programs, and applications. Like Basic, Fortran, editors, but also games.

Hands On: reboot the PiDP to DECTape configuration: set IF field to octal 3, then toggle Sing_Step and set IF switches back to 000. This mounts a bootable OS/8 dectape, with system utilities and Fortran. Booting from tape takes a good few seconds (tape is supposed to be slow, but for simh experts: this boots from dt0, not td0. So the slowness of real tapes is properly emulated!). You are then presented with the command line prompt (.). Enter DIR to see what's on the tape. After a good few seconds more, you'll see the directory. Let's compile the TEST.FT Fortran program:

Introduction: although DECtapes were a huge improvement over paper tape, with OS/8 and block-oriented file systems now possible, it remains a slow process. With the introduction of hard disks and 8" floppy disks, the PDP-8 entered the modern era. Now, using OS/8 does not feel very different from CP/M or early MS-DOS systems in terms of speed and - dare we say - capabilities.

Hands On: Reboot into OS/8 by setting the IF switches to 111, and toggle Sing_Step. This mounts and boots an RK05 disk cartridge with OS/8 on it. There are two partitions, so just typing DIR will show you only the directory of the first one. DIR RKB0: will show the many games and utilities on the second one.

Try to run the classic Colossal Cave adventure, see here: Tangentsoft PiDP-8 ADVENT
Run the Game of Life using R BASIC, OLD, RKB0:LIFE, RUN. Use Ctrl-C and BYE to return to OS/8.
Do what was long thought impossible: write a C program on a PDP-8. Ian Schofield wrote one in 2017: CC8 C compiler. You might want to use a Linux editor and copy the source code over to OS/8, until you've learned the teco editor. See further down.

Introduction: Spacewar! was the first video game ever. And a good one. Originally written for the PDP-1 in 1962, it was ported to quite a few other machines over the years. The PDP-8, it seems, got its definitive version in 1974, and required a vc8i oscilloscope display or vc8e point-plot display option. Originally, spacewar! used front panel switches, which was not a good idea as it wore them out quickly. So, typically, custom-made controllers were made to properly play the game.

Hands On: These are not computer displays as we know them today. The VC8-E generates a picture by the processor specifying an X and Y location and then requesting that a spot be drawn on the CRT. It then repeated this process to draw the entire display out of a bunch of dots. 60 times a second.

In 2015, Kyle Owen made a VC8-E simulator to be used with SimH. You can either run it remotely on a PC that acts as an X/Y CRT, connected to the PiDP. Alternatively, run a Pi-specific version of the vc8e emulator on the PiDP itself, and the HDMI port of the PiDP itself can be used.

Introduction: We're blurring the time line by the mention of the year 1975. TSS/8 had been around since 1968, and performed an astonishing feat: an 8 (32, if you insisted) user multitasking operating system allowing you to log in on multiple terminals, giving each user a full 20K virtual PDP-8, despite the hardware only having 32K words in total. It provides Basic, Focal, editor and assembler and more out of the box. If you define the concept broadly, it does email too... Once you've mastered TSS/8, take away the PCs of seven of your work colleagues and let them log in to TSS/8 user sessions on the PiDP. There is nothing more you need to run your company than a single PDP-8 with TSS/8 offers, with a bit of home study. Prepare to hire more competent staff soon though.

Hands On: Set the IF switches to octal 2 and toggle Sing_Step. This will boot TSS/8, and ask you the following:

Introduction: There were 10 implementations of the PDP-8 design over its life span of 15 years. The 8/I was built using only simple 74 logic chips, but the Straight Eight only used discrete components (diodes, transistors). The last few models actually moved on to use a microprocessor with the PDP-8 logic inside. Now think of SimH as the 11th implementation of the PDP-8 design. It may be done in software, but the PDP-8 always was a computer architecture, not a single hardware design. Yes, there will always be a yearning to run Real PDP-8 Hardware. But SimH is the best implementation of the PDP-8 architecture to date... Set breakpoints, disassemble on the fly - the kind of stuff that programmers back in the day would have given an arm and a leg for.