Re: [Simh] Bliss versus C

[Johnny Billquist]

On 2018-01-30 16:15, Clem Cole wrote:



On Tue, Jan 30, 2018 at 9:45 AM, Johnny Billquist > wrote:


  if they had been able to get a pdp-10 then Unix would not have
happened.


​That was Ken describing the Tenex development in the introduction to 
his Turning award: /"I suspect Daniel Bobrow would be here instead of me 
if he could not afford a PDP-10 and had to "settle" for a PDP-11."/


https://www.ece.cmu.edu/~ganger/712.fall02/papers/p761-thompson.pdf 



Ah. Right. That was what my memory was trying to remember.

  Johnny

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Re: [Simh] BLISS and C

[Dave Wade]

> -Original Message-
> From: Simh [mailto:simh-boun...@trailing-edge.com] On Behalf Of Phil
> Budne
> Sent: 30 January 2018 00:17
> To: simh@trailing-edge.com
> Subject: Re: [Simh] BLISS and C
> 
> > I also think that Dave was asking for a B compiler, and not a BCPL 
> > compiler...
> 

Yes

> Amongst the PDP-7 UNIX files was a B runtime, which someone on the team
> was able to decipher well enough to write a B compiler in a C
> subset:
> 
> https://github.com/DoctorWkt/pdp7-unix/blob/master/tools/b.c
> 
> And then make self-hosting, in:
> https://github.com/DoctorWkt/pdp7-unix/tree/master/src/other
> 
> ISTR, the compiler generates something like more threaded code, as
> opposed native instructions, but the output is fed to the assembler (along
> with runtime source) to make an executable.
> 

Sounds like an interesting project... 

> A paper I first saw VERY recently describes Thompson bringing up the B
> interpreter on the CPU of a Merganthaller phototypsetter (since the vendor
> supplied S/W was too limited for them to use).
> 
> Ah:
> https://www.cs.princeton.edu/~bwk/202/summer.scanned.pdf
> document p8 (pdf p9)
> 
> ... KLT resurected the B interpreter.  B is a good language for a
> 16-bit word-oriented minicomputer, and most of our subsequent 202
> programs have been written in B.
> ___

I will have a look at that


> Simh mailing list
> Simh@trailing-edge.com
> http://mailman.trailing-edge.com/mailman/listinfo/simh

Dave


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Re: [Simh] Bliss versus C

[Clem Cole]

On Tue, Jan 30, 2018 at 9:45 AM, Johnny Billquist  wrote:

>  if they had been able to get a pdp-10 then Unix would not have happened.
>

​That was Ken describing the Tenex development in the introduction to his
Turning award: *"I suspect Daniel Bobrow would be here instead of me if he
could not afford a PDP-10 and had to "settle" for a PDP-11."*

 https://www.ece.cmu.edu/~ganger/712.fall02/papers/p761-thompson.pdf


 Clem
​
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Re: [Simh] Bliss versus C

[Johnny Billquist]

I think he said something similar about if they had been able to get a pdp-10 
then Unix would not have happened.

  Johnny 


dave porter  skrev: (30 januari 2018 05:12:10 CET)
>Clem Cole wrote:
>
>>Hmmm.. to be honest this sound nice but I suspect it is more like
>>legend/wishful thinking than something Dennis would have said.
>
>I'm pretty sure I read this in something actually written
>by Ritchie, though since I can't come up with the source,
>it's possible I'm suffering from uncorrectable memory errors.
>
>
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Re: [Simh] BLISS and C

[Jordi Guillaumes Pons]

Jordi Guillaumes i Pons
j...@jordi.guillaumes.name
HECnet: BITXOW::JGUILLAUMES


> 
> I was also going to point out that neither {} nor [] exist in (System/360 era)
> EBCDIC, so could not have been used in PL/1.
> 
> PL/1 (or PL/I, to use the later naming convention) has both BEGIN/END and
> DO/END, with different effects.  I got a long lecture from an office mate once
> about a program which was using BEGIN/END where DO/END was preferable, because
> BEGIN blocks actually create a new context, with internal/external scope
> details, while DO blocks do not create a new context.

There are no curly braces on any PL/I version that I’m aware of. 

The “normal” way to build statement blocks is DO/END, with are just combined 
statements (so can be used in IF…ELSE… or WHILE blocks; PL/I has no ‘END IF nor 
‘END WHILE’ statements). BEGIN/END create a semantic context where you can 
define local variables or, more usefully, establish local condition handlers.

A way to do a controlled check for overflow is, for instance

…
BEGIN;
DECLARE IS_OVERFLOW BIT(1) INIT(‘0’B);
ON OVERFLOW IS_OVERFLOW = ‘1’B;
NUMBER = BIGNUMBER1 + BIGNUMBER2;
IF IS_OVERFLOW THEN CALL HANDLE_OVERFLOW();
END;
…

That “ON” condition is only valid inside the BEGIN/END block, so if an OFL 
condition occurs elsewhere (and you have used the correct compiler options) the 
program will crash (“ABEND”, in IBM idiom). That is actually what you really 
WANT to happen (better to get a call at 3am than to have to correct a corrupt 
file).




Jordi Guillaumes i Pons
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Re: [Simh] BLISS and C

[Phil Budne]

> I also think that Dave was asking for a B compiler, and not a BCPL compiler...

Amongst the PDP-7 UNIX files was a B runtime, which someone on the
team was able to decipher well enough to write a B compiler in a C
subset:

https://github.com/DoctorWkt/pdp7-unix/blob/master/tools/b.c

And then make self-hosting, in:
https://github.com/DoctorWkt/pdp7-unix/tree/master/src/other

ISTR, the compiler generates something like more threaded code, as
opposed native instructions, but the output is fed to the assembler
(along with runtime source) to make an executable.

A paper I first saw VERY recently describes Thompson bringing up the B
interpreter on the CPU of a Merganthaller phototypsetter (since the
vendor supplied S/W was too limited for them to use).

Ah:
https://www.cs.princeton.edu/~bwk/202/summer.scanned.pdf
document p8 (pdf p9)

... KLT resurected the B interpreter.  B is a good language for a
16-bit word-oriented minicomputer, and most of our subsequent 202
programs have been written in B.
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Re: [Simh] BLISS and C

[Phil Budne]

Rich Alderson wrote:
> Ken had no tools for the PDP-7, which was part of a Graphics-1 setup (with a
> Type 340 display)

A nit, but I think the display controller was Bell designed, custom
hardware.  PDP-7 UNIX used it as a glass TTY (independent from the
console TTY).  I simulated JUST enough of it (character display,
keyboard and auto-pressing the clear screen key) in SIMH so that you
can have two users active!  I worked from BTL documents to implement
the simulation.

Since the world has changed so much since I did the original XY
display code that's now integrated into SIMH (tho I wrote it to be
simulator agnostic and stand-alone), I thought about making a Web UI
that lit the light that says "display list memory area full", and
forced the user to click on an HTML button to clear the screen!

It seemed like the majority of Graphics-1 systems built were PDP-9's
so it's possible the PDP-7 was a cast-off prototype.

Somewhere I've a description of the Graphics system being as large as
the PDP-7 itself. In addition, ISTR the disk system cost as much as
the CPU (I think the same type of disk was also used as a swap device
on KA10 timesharing systems), and fast enough to swap the high half
(4K) of memory in/out for each process painlessly.  ISTR that one or
both of the above recollections were from Doug McIlroy

Phil
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Re: [Simh] BLISS and C

[Johnny Billquist]

On 2018-01-29 23:48, Timothe Litt wrote:

On 29-Jan-18 17:45, Dave Wade wrote:

-Original Message-
From: Simh [mailto:simh-boun...@trailing-edge.com] On Behalf Of Bob
Eager
Sent: 29 January 2018 22:08
To: simh@trailing-edge.com
Subject: Re: [Simh] BLISS and C

On Mon, 29 Jan 2018 12:05:01 -0500
Clem Cole <cl...@ccc.com> wrote:


One can argue, why did Ken not just build something more like BCPL
instead of B?  I can not say, maybe the brevity of { } from PL/1 was
more attractive than the Algol BEGIN/END style?

BCPL was, in any case, using $( $) and (later) { }. It never used BEGIN/END.


The "B" compiler I used on the Honeywell L6000/L66 used { }.


And the major drawback of BCPL (which I love) was that it was word
oriented. Most machine architectures were not (OK, PDP-10...) One had to
use contortions, and a special % operator, to access bytes efficiently.


"B" is similar, characters were accessed by functions rather than a special 
operator, but you can, I think use a combination of shifts and logical operators
... those familiar with BCPL or C who have not encountered B may find the 
manual here interesting...

https://www.bell-labs.com/usr/dmr/www/bref.html

it would be nice to find a working compiler for a word based machine...


I seem to remember that there was a BCPL for TOPS-10 in the DECUS library.


I have a BCPL compiler for RSX, which also came from DECUS. Now, the 
PDP-11 is probably not a word based machine in the sense Dave meant.
However, I also think that Dave was asking for a B compiler, and not a 
BCPL compiler...


  Johnny

--
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  ||  on a psychedelic trip
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Re: [Simh] BLISS and C

[Timothe Litt]

On 29-Jan-18 17:45, Dave Wade wrote:
>> -Original Message-
>> From: Simh [mailto:simh-boun...@trailing-edge.com] On Behalf Of Bob
>> Eager
>> Sent: 29 January 2018 22:08
>> To: simh@trailing-edge.com
>> Subject: Re: [Simh] BLISS and C
>>
>> On Mon, 29 Jan 2018 12:05:01 -0500
>> Clem Cole <cl...@ccc.com> wrote:
>>
>>> One can argue, why did Ken not just build something more like BCPL
>>> instead of B?  I can not say, maybe the brevity of { } from PL/1 was
>>> more attractive than the Algol BEGIN/END style?
>> BCPL was, in any case, using $( $) and (later) { }. It never used BEGIN/END.
>>
> The "B" compiler I used on the Honeywell L6000/L66 used { }.
>
>> And the major drawback of BCPL (which I love) was that it was word
>> oriented. Most machine architectures were not (OK, PDP-10...) One had to
>> use contortions, and a special % operator, to access bytes efficiently.
>>
> "B" is similar, characters were accessed by functions rather than a special 
> operator, but you can, I think use a combination of shifts and logical 
> operators
> ... those familiar with BCPL or C who have not encountered B may find the 
> manual here interesting...
>
> https://www.bell-labs.com/usr/dmr/www/bref.html
>
> it would be nice to find a working compiler for a word based machine...

I seem to remember that there was a BCPL for TOPS-10 in the DECUS library.





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Re: [Simh] BLISS and C

[Dave Wade]

> -Original Message-
> From: Simh [mailto:simh-boun...@trailing-edge.com] On Behalf Of Bob
> Eager
> Sent: 29 January 2018 22:08
> To: simh@trailing-edge.com
> Subject: Re: [Simh] BLISS and C
> 
> On Mon, 29 Jan 2018 12:05:01 -0500
> Clem Cole <cl...@ccc.com> wrote:
> 
> > One can argue, why did Ken not just build something more like BCPL
> > instead of B?  I can not say, maybe the brevity of { } from PL/1 was
> > more attractive than the Algol BEGIN/END style?
> 
> BCPL was, in any case, using $( $) and (later) { }. It never used BEGIN/END.
> 

The "B" compiler I used on the Honeywell L6000/L66 used { }.

> And the major drawback of BCPL (which I love) was that it was word
> oriented. Most machine architectures were not (OK, PDP-10...) One had to
> use contortions, and a special % operator, to access bytes efficiently.
> 

"B" is similar, characters were accessed by functions rather than a special 
operator, but you can, I think use a combination of shifts and logical 
operators
... those familiar with BCPL or C who have not encountered B may find the 
manual here interesting...

https://www.bell-labs.com/usr/dmr/www/bref.html

it would be nice to find a working compiler for a word based machine...

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Dave

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Re: [Simh] BLISS and C

[Bob Eager]

On Mon, 29 Jan 2018 12:05:01 -0500
Clem Cole  wrote:

> One can argue, why did Ken not just build something more like BCPL
> instead of B?  I can not say, maybe the brevity of { } from PL/1 was
> more attractive than the Algol BEGIN/END style?

BCPL was, in any case, using $( $) and (later) { }. It never used
BEGIN/END.

And the major drawback of BCPL (which I love) was that it was word
oriented. Most machine architectures were not (OK, PDP-10...) One had
to use contortions, and a special % operator, to access bytes
efficiently.

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Re: [Simh] BLISS and C

[Richard Cornwell]

> On Mon, 29 Jan 2018 16:35:42 -0500 (EST)
> Rich Alderson  wrote:
>
> > From: Clem Cole 
> > Date: Mon, 29 Jan 2018 14:21:36 -0500  
> 
> > My point was less on PL/1 and more to the point that Ken had access
> > to BCPL and did not have BLISS.   But he still decided to create
> > what would become B.  
> 
> Ken had no tools for the PDP-7, which was part of a Graphics-1 setup
> (with a Type 340 display), not even an assembler.  The first thing he
> wrote on the GECOS system (not yet shortened to GCOS, since it was a
> GE 635) was an assembler, which shared absolutely nothing in terms of
> syntax with the DEC assembler for the system.
> 
> Remember that BCPL originated on a PDP-7, and had an 18-bit word as
> its only data type.  Since Ken had only a cross assembler to start
> with, B was the simplest interim solution (a BCPL subset in an
> interpreter).

  BCPL originated on the IBM 7090 under CTSS. It only supported 36 bit
  word data types. I am not sure BCPL was ever ported to the PDP-7. 

Rich

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Re: [Simh] BLISS and C

[Rich Alderson]

> From: Clem Cole 
> Date: Mon, 29 Jan 2018 14:21:36 -0500

> My point was less on PL/1 and more to the point that Ken had access to BCPL
> and did not have BLISS.   But he still decided to create what would become
> B.

Ken had no tools for the PDP-7, which was part of a Graphics-1 setup (with a
Type 340 display), not even an assembler.  The first thing he wrote on the
GECOS system (not yet shortened to GCOS, since it was a GE 635) was an
assembler, which shared absolutely nothing in terms of syntax with the DEC
assembler for the system.

Remember that BCPL originated on a PDP-7, and had an 18-bit word as its only
data type.  Since Ken had only a cross assembler to start with, B was the
simplest interim solution (a BCPL subset in an interpreter).

Rich
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Re: [Simh] BLISS and C

[Rich Alderson]

> From: Paul Koning 
> Date: Mon, 29 Jan 2018 13:33:30 -0500

>> On Jan 29, 2018, at 12:05 PM, Clem Cole  wrote:

>>  ...  One can argue, why did Ken not just build something more like BCPL
>> instead of B?  I can not say, maybe the brevity of { } from PL/1 was more
>> attractive than the Algol BEGIN/END style?

> PL/I has begin/end as ALGOL does.  I don't know where { } came from, but it
> isn't from PL/I.  What perhaps did come from PL/I is ; as terminator rather
> than separator.

I was also going to point out that neither {} nor [] exist in (System/360 era)
EBCDIC, so could not have been used in PL/1.

PL/1 (or PL/I, to use the later naming convention) has both BEGIN/END and
DO/END, with different effects.  I got a long lecture from an office mate once
about a program which was using BEGIN/END where DO/END was preferable, because
BEGIN blocks actually create a new context, with internal/external scope
details, while DO blocks do not create a new context.

(The thing is, I was writing in Pascal, not PL/I, where begin/end works like
 PL/I's DO/END, but the rant was interesting enough that I let him run to
 competion before pointing that out to him.  Was that behavior new to Pascal,
 or inherited from Algol 60?)

Rich
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Re: [Simh] BLISS and C

[Clem Cole]

On Mon, Jan 29, 2018 at 1:33 PM, Paul Koning  wrote:

>
> PL/I has begin/end as ALGOL does.  I don't know where { } came from, but
> it isn't from PL/I.  What perhaps did come from PL/I is ; as terminator
> rather than separator.


Fair enough, although I will say I had a PL/1 style/dialect compiler from
my IBM days that I thought I remember allowing it - which may have been
BCPL, PL/360 or maybe even PL/C -- too many beers ago.  I was never much of
a PL/1 programmer, and I could easily be mushing it all together.  Most of
my 360 hacking in those days was in assembler.

FYI:  Check out:  http://www.bobbemer.com/BRACES.HTM for an interesting
discussion of curly braces.

I do sort of remember the $( and $) digraphs as IIRC the one of the
keypunch (??19?? I think)  could not create them but the ??26?? could.
Thinking
about it... it may have been that the later was allowed for BEGIN/END in
the PL/x dialect and then later Ken switched from the BCPL digraph to curly
braces.

My point was less on PL/1 and more to the point that Ken had access to BCPL
and did not have BLISS.   But he still decided to create what would become
B.

Clem

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Re: [Simh] BLISS and C

[Paul Koning]

> On Jan 29, 2018, at 12:05 PM, Clem Cole  wrote:
> 
> ...
> One can argue, why did Ken not just build something more like BCPL instead of 
> B?  I can not say, maybe the brevity of { } from PL/1 was more attractive 
> than the Algol BEGIN/END style? 

PL/I has begin/end as ALGOL does.  I don't know where { } came from, but it 
isn't from PL/I.  What perhaps did come from PL/I is ; as terminator rather 
than separator.

I was looking at ALGOL syntax again recently, and noticed something 
interesting: the ALGOL-60 procedure declaration syntax is nearly identical to 
the K style function declaration syntax in C.  That is, this style:

foo (a,b);
int a, b;
{ /* ... */ }

looks just like what ALGOL-60 uses.

paul


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Re: [Simh] BLISS and C

[Clem Cole]

On Mon, Jan 29, 2018 at 8:20 AM, dave porter 
wrote:

> I recall reading something from Dennis Ritchie to the effect
> that if he'd been able to get hold of a BLISS compiler he
> wouldn't have bothered to invent C.  But DEC held on to
> its compilers tightly.


​Hmmm.. to be honest this sound nice but I suspect it is more like
legend/wishful thinking than something Dennis would have said.
Unfortunately we can not ask him, but I can report a little on how both
languages came into being (actually all three cause you need to include B
here also) as I know/knew the designers of both and was a witness to a
small portion of the stories.  You can then decide for yourself.

Two related things that I did not mention yesterday when I was describing
the differences between the languages are that BLISS has only one data type
(a 'word') and is 'typeless' in the sense of Pascal or other strongly typed
languages.   C was originally 'weakly typed' and only later added strong
typing (and why is important).  Also remember that at the time BLISS was
designed, Wulf specifically targeted the PDP-10(the PDP-11 did not yet exist
and the PDP-8 was explicitly a non-target).  I'm pretty sure if you read
Wulf's original paper, they were not trying to be
architecture independent.  Also it was designed to be an >>implementation<<
language for the PDP-10.  Another point is that Wulf and team had other
tools for the PDP-10 when they wrote it - including an OS.

B (C direct predecessor), like BCPL and BLISS, was untyped and worked with
words only.   In fact, Ken is on record as saying that he was originally
starting to develop a Fortran compiler for the PDP-7 to run on UNIX (both
of which had been written in PDP-7 assembler).   He ended up with a new
semi-interpreted language that was good enough to write utilities; i.e. B
was born and started a life of its own.  He was clearly influenced by BCPL
and had just been using PL/1 with Multics.   Clearly he was trying to
create an implementation language for the PDP-7.  But Ken was not using any
tools other than his own for the PDP-7 - in fact he was originally cross
assembling from a GECOS system.Once UNIX was 'up' on the PDP-7, it
was minimal compared to TOPS-10, that Wulf had used [check out:  pdp7-unix
is a project to resurrect Unix on the PDP-7
].

BTW: another salient point is that Ken, Dennis and team had previously
tried to purchase a PDP-10 for their lab, and had been rejected by their
management.   The whole reason Ken was working on the PDP-7, was that he
borrowed it from another group and he had access to it.   They were using
GCOS as their 'main systems' and the PDP-7 system was being developed as
an independent project.

So by the time of moving Unix to PDP-11, Dennis had switched from an
B interpreter to a B compiler; which then begat NB, ney C [See Clem Cole's
Quora answer What-language-was-the-first-C-compiler-written-in
].
  So the point is that Dennis was building tools to support their project
and C was just continuing the development of Ken's B.

One can argue, why did Ken not just build something more like BCPL instead
of B?  I can not say, maybe the brevity of { } from PL/1 was more
attractive than the Algol BEGIN/END style?   I don't know.   But I suspect
it was because he was originally targeting Fortran that he kept 'blocks' to
be minimal.   He ended up with something like BCPL in semantics and PL/1 in
syntax than Fortran.

Back to C:  With the PDP-11 Dennis added supports for different data types
- in particular bytes and byte addressing.   Originally, he left the C
language mostly typeless (everything defaulted to an int).  C stays that
way for a long time, through K   But as the language starts to get used
for other architectures, the ideas of being 'more strongly typed' starts to
come into play.   In fact, I think the two primary changes to ANSI C that
helped to cement C in the long run, were strong typing and function
prototypes (which used it).

As I think back on Wulf's intention to create a systems programming
language with good support for SW engineering, and I suspect the single
'word' and lack of typing actually would have hurt Bill's claimed intent
for BLISS (I've never asked him - I need too next time I see him).

All this comes back to my point.   Btw the time Dennis develops, C, B had
been in use and had been created incrementally from B.   If Ken had had
access to BLISS compiler, he would have needed it on GCOS, and CMU never
created same and then you are correct, sold the rights to their
implementations to DEC.  But the fact is, Ken and Dennis did have a BCPL
compiler on GCOS?  So why not just retarget it to the PDP-7?   Why did Ken
create B?

Clem


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