My Vintage Dream PC

This is a good thing. When was it released?

-- Patrick

 

Most CS departments have an undergrad class in compiler writing, in
which the term project is to write (for a toy language, of course).
They don't write it in machine code!

 

The bad thing is that it's proprietary storage with no
available documentation on the storage format (at least there wasn't when I
used ClearCase). It was also fragile when I used it and hard to set up. It
may have improved but using it made me think fondly of CVS.

 

I suspect getting time on one of those 5 computers would be like
getting observation time on the hubble.

I should ask around the MV plant and see if there's anyone left that
remembers.

scott

 

IIRC, 20 years ago. I believe it started on the Apollo systems.

It would only be a good thing if it were open source, never a good
idea to trust your crown jewels to a proprietary file(system) format; will
almost always bite you in the end.

scott

 

Sigh.

-- Patrick

 

I don't know about PDP's, but the minis I built (based on
GA SPC-16) had 3 backplanes: CPU, I/O, EXPANDED MEMORY.
When building the complete computer, they would be brought
up in that order. The bootstrap ROM was part of the EXPANDED
MEMORY, which required a controller in the I/O backplane.

The ASR33 was connected directly to the CPU backplane, so I
spent a good portion of my life toggling in the papertape
bootstrap loader (6 16-bit words) which I eventually
memorized. Not because I wanted to, just from having done
it so often. One day, after leaving that company, I woke
up and suddenly realized I had forgotten the papertape
bootstrap!

What a great feeling, like being released from the French
Foreign Legion.

 

Write a c compiler in c is the basic exercise.

 

That's a bigger exercise than needed to get the point across. When I
taught the class a couple of times I defined a small subset of C I
called Cb (pronounced C flat); it wsa written in C, lex, and yacc, and
generated Motorola HC11 code.

 

It cannot be a basic exercise if one is writing in C. Tee hee hee...

 

I "researched" this before and received the following information:

In "KSNJFL", each letter was represented by the correct decimal value
in the five-level teletype code that communicated with the computer.
The computer input was mainly paper tape produced by teletype.

Charlie Jones of the University of Iowa sent the following to me in
an email:

Here is the 5-level code used by Illiac, transcribed from THE ILLIAC
MINIATURE MANUAL, by John Halton, Digital Computer Laboratory File 260,
University of Illinois, Urbana, 1958, page 3. I have preserved the
layout as much as is possible using ASCII:


THE TAPE CODE
-------------
| Characters | n for 92 | Characters | n for 92
Tape Holes | F/S | L/S | Orders Tape Holes | F/S | L/S | Orders
---------------------------------- ----------------------------------

| o | 0 P 2F |O o | Delay Delay 3F
| o O| 1 Q 66F |O o O| $(Tab) D 67F
| o O | 2 W 130F |O o O | CR/LF CR/LF 131F
| o OO| 3 E 194F |O o OO| ( B 195F
| oO | 4 R 258F |O oO |L/S=Letter-Shift 259F
| oO O| 5 T 322F |O oO O| , V 323F
| oOO | 6 Y 386F |O oOO | ) A 387F
| oOOO| 7 U 450F |O oOOO| / X 451F
| Oo | 8 I 514F |OOo | Delay Delay 515F
| Oo O| 9 O 578F |OOo O| = G 579F
| Oo O | + K 642F |OOo O | . M 643F
| Oo OO| - S 706F |OOo OO|F/S=Number-Shift 707F
| OoO | N N 770F |OOoO | ' H 771F
| OoO O| J J 834F |OOoO O| : C 835F
| OoOO | F F 898F |OOoOO | x Z 899F
| OoOOO| L L 962F |OOoOOO| Space Space 963F

 

So you just read books, wrote your own compiler, turned it in, and got
a grade??? *No* one was teaching you any of this???

 

Isn't it *more* difficult to produce code for the 8-bit HC-11 than
it would be for the MC68000 ??? The MC68000 has a reasonable assembly
language/machine language for producing code. You can use actual
multiply and divide instructions rather than writing your own multiply
and divide *routines*. (You probably *gave* the students those routines
to call from the compiler binary output.)

And how about linkage to functions??? You *did* have functions???

 

I had a friend who was a grad student. Once he went into the
department office and asked the secretary for some "dildo paper".
She just handed him some ditto paper and said nothing.

 

The HC11 has the huge advantage that it's the machine we use in our
assembly language class (we have them build a SBC and control LEGO
robots with it), so the students already know it and they know the
simulator we use for it.

It's also got multiply and divide instructions. The thing about a toy
language for a class, though is that if it didn't have them, the
language could be defined to not have them either (you have to have
enough operations to exercise operator precedence, but bitwise boolean
operations would suffice for that).

It's got push and pop instructions, pushes return addresses on the
stack, does indexed addressing....

 

Dr. Freud, paging Dr. Freud to the white courtesy phone...

 

It's still proprietary. There might be some hope that the client side
will be opened now that IBM owns rational. They would still get the
money from the server side, and the client-computer support would be
easier.

CC is sometimes fragile, it needs administration. But on the other hand
it supports many features that the others don't. For example the
building avoidance is a nice feature in big environments i.e. if the
versioned file is already compiled in someones view it is just copied
over, not compiled.

CVS is something I don't like, SVN is CVS with steroids, but still quite
old fashioned. Especially branching etc. is quite bad in CVS, and was
quite bad in SVN until recently. But still ClearCase is much better if
huge amount of branches, labels etc is used. I also like the idea of the
new distributed VCS systems (git, bitkeeper etc.), they are the future I
would say. In distributed systems the single points of failure
are not there, and they scale nicely with the amount of developers.

--Kim

 

Being fragile was an instant death issue for me - a VCS must not
lose data *ever*, when I tried it CC lost whole projects.

Scary - compilation is often sensitive to the environment.

Yes it is - but then I prefer to keep branching to a minimum and
use the "develop in head and merge to release branch" approach rather than
the "develop in a branch and merge to head" which I find to be unmanageable
no matter what tools are used.

You may well be right, although AFAIK they all lose the nice
feature of CVS that the RCS files it uses are readable and easily found. In
extremis you can even repair an RCS file with vi if you manage to break one
somehow.

 

This was in the late 60s and the system was an IBM 1620.

/BAH

 

What books? I don't recall ever seeing a text book.

Not turned it in. Demo'ed it.

No grade. The compiler either worked or it didn't. When it worked,
you got an A.

I never got to take the class. and there wasn't anybody to
teach it. The people who did write one learned as they went.
They knew how a compiler was supposed to work because we had
FORTRAN II on the system.

/BAH