How to make use of the transcribed listing?

[larsbrinkhoff]

Hello,

Is there a plan for making use of the transcribed listing?

Is there a cross assembler? Is there a JOHNNIAC emulator?

[sebras]

There are several instruction listings and I'm working on an emulator for JOHNNIAC. I'm using what appear to be sample tests to see if the emulator behaves reasonably. I'm basically slowly teaching myself how to write an emulator. If I can get anything to run decently there I might have learned enough to make a port of it to SimH. That's my plan anyway.

There is an assembler written for JOHNNIAC itself, JACASS II. Since JACASS II appears to be written in its own assembler format it is rather hard to put into the emulator. I have seen a document somewhere that explains the format, but where is it now? Oh and I have not fully understood the format yet.

[larsbrinkhoff]

Cool! I'd like to see your emulator when there is something to show.

I might be interested in making an assembler. In addition to making an executable binary, it could also do some sanity checks on the transcribed text. Perhaps Python would be comfortable implementation language for many?

Just by typing some pages, I'm guessing this:

                       vOperand 1, register Q5
G006E000+    * 33  010 Q  5 010 * 043
^Page ^ ^    ^Label ^Opcode     ^Operand 2, memory?
   Line New section?
```

P and Q seems to be registers?  * memory?  = immediate?

[larsbrinkhoff]

Ah, this explains a lot.

[drboone]

The JOSS listing is in J136 loader format. http://bitsavers.org/pdf/rand/johnniac/J136A_Loader_For_Style_E_Programs_Dec55.pdf

[drboone]

Also, the JACASS pdf is an actual assembler listing, with both source and object represented. It ought to be possible to convert the object code columns into one of the absolute binary card formats fairly easily.

[sebras]

The JOSS listing is in J136 loader format. http://bitsavers.org/pdf/rand/johnniac/J136A_Loader_For_Style_E_Programs_Dec55.pdf

I have that loader transcribed.

[sebras]

The JOSS listing is in J136 loader format. http://bitsavers.org/pdf/rand/johnniac/J136A_Loader_For_Style_E_Programs_Dec55.pdf

I have that loader transcribed.

This is now part of #13.

[sebras]

In #2 I read

I haven't seen much (any?) doco about how the machine was initially started. Anyone? My guess is that a short series of 10.x orders were entered from the console to initially load a card deck (or perhaps something stored permanently on the drum).

I have not seen anything about that. But it seems like JOHNNIAC had a number of subroutines (listed in http://www.bitsavers.org/pdf/rand/johnniac/Johnniac_Library_Writeups_Sep59.pdf) saved in some (semi-?)permanent locations such that their addresses could be depended on.