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Andrew Herbert

Oct 12, 2022, 2:12:26 PM10/12/22
to PiDP-8
I cannot get FORTRAN IV programs to execute.

I have tried the PEP001 example and an even more simple

      WRITE (4, 100)
100   FORMAT (' hello world')

In each case

.R F4

produces a listing, shows the loader doing its stuff and takes me to a * prompt.  Typing ESC sends my pipdp8i off computing but I never get to see any output.

If I break out with ^C and try to rerun with 


I get the same behaviour.

Any suggestions for what the problem might be?


Rick Murphy

Oct 12, 2022, 2:45:48 PM10/12/22
to Andrew Herbert, PiDP-8
Is that source real? Lower case strings aren't supported, so that'll do weird things. (But it should be consistent.)
Here's what I get:

100     FORMAT(' hello world')


(%,,/ 7/2,$

If you're not getting anything at all, and just a hung system, then there's something bad on your OS/8 disk.
One of the issues with some of the homebrew OS/8 disks are disjoint versions of the FORLIB.RL and FRTS.SV, leading to bad behavior at run time. What's the provenance of your media?
The work done by Bill Cattey and friends to ensure that the media is all built from known good sources eliminates this kind of mismatch potential.

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Rick Murphy, D. Sc., CISSP-ISSAP, K1MU/4, Annandale VA USA

Ian Schofield

Oct 12, 2022, 5:15:13 PM10/12/22
to PiDP-8
Dear All,

 Even F4 does not like lower case text.
20      FORMAT('A test line')
        CALL EXIT


 4%34 ,).%


This is the general case for most (if not all) PDP8 languages.
Typically, ASCII is stored in packed 6bit codes (2 per 12 bit word)
as a result, the character set is limited....
However, OS/8 itself stores ascii in packed 8 bit characters (3 per 2*12 bit words)
So, you can edit files containing lower case chars but don't expect compilers to do much with them.
NB: the Basic editor doesn't even let you enter LC chars!!!

Regards, Ian

Andrew Herbert

Oct 12, 2022, 6:59:05 PM10/12/22
to PiDP-8
The source code on the PiDP8i is all upper case - my miscopy is a read herring.

So it sounds like something is broken on my emulated RK05.  It started as a copy of the current standard RK05 in the distribution, but I have been using for several weeks so something might have got smashed.

I'll try on a clean copy.


Randy James

Oct 12, 2022, 7:26:03 PM10/12/22
to Ian Schofield, PiDP-8
In the late 70’s I wrote a WYSIWUG word processor for TSS/8 and Vt52s…with the ability to display upper and lower case.  We had a 96 character drum on our Lp08 line printer.   Ahead of my time…

On Oct 12, 2022, at 4:15 PM, Ian Schofield <isy...@gmail.com> wrote:

Dear All,

Steve Tockey

Oct 13, 2022, 11:21:14 AM10/13/22
to PiDP-8

I see several possible problems:

1) When you are compiling, you aren't saving the .RL output from F4. The first parameter of the line after R F4 is supposed to be the name of the.RL output from F4 but since there is a comma first the .RL output is not generated.

2) You need to link the .RL file using the LOAD program to make a .LD file that FRTS uses.

3) Don't use the < as the input spec for FRTS

In other words, the following should work better:

.R F4



I would highly recommend that you look a the F4 section in the OS/8 Language Reference Manual available here:


-- steve

Andrew Herbert

Oct 14, 2022, 1:54:58 PM10/14/22
to PiDP-8
Hi Steve,

Your recipe dug me out of the hole I was in.  Thanks for the pointer to the Programming Languages Reference Manual.  I was working from the OS/8 System Handbook which is a bit abbreviated.

I've now resurrected a bunch of old FORTRAN IV programs and made them run on the PiDP8.


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