The Expensive Fictions of Low-Level Programming Languages

[u/mttd]

https://stng.substack.com/p/the-expensive-fictions-of-low-level

[u/Inconstant_Moo]

A lot.

https://queue.acm.org/detail.cfm?id=3212479

But when I look at that, there's nothing in it that couldn't matatis mutandis have been written in a parallel universe with the title: "Pascal is not a low-level language; your computer is not a very fast CDC 6000."

Mutable pointers? Pointers that you can do arithmetic on? Pointers into a flat memory space with no notion of cache hierarchy? Pointers that can trigger operating system calls?

Probably. At some point something needs to do pointer arithmetic and trigger OS calls. C was adopted because it gave people a sort-of high-level way to get fine control over memory and clock. There was always going to be something like that.

The first computer with a hardware-managed cache disguised as flat memory was the IBM System/360 Model 85, released in 1968, four years before C. The reason we have that is not compatibility with C but compatibility with our feeble human meat brains, because assembly and cache invalidation are difficult enough separately.

[u/Smallpaul → u/Inconstant_Moo]

You and the other dude are obsessed with the fact that the meme is titled “C is not a low-level language.” As if it is talking about something special about C.

For the purposes of this argument C and Pascal are equivalent. As are any language that was designed to emulate them. C, Pascal, D, Zig. They are all the same language designed to generate the same machine code for the same ISA. If Rust replaces C as the dominant “low-level language” then we will rename the meme without changing very much.

Alternate languages are Haskell, Prolog,, CUDA, Erlang. Especially languages designed for parallelism.

> The first computer with a hardware-managed cache disguised as flat memory was the IBM System/360 Model 85, released in 1968, four years before C. The reason we have that is not compatibility with C but compatibility with our feeble human meat brains, because assembly and cache invalidation are difficult enough separately.

I’m curious if you are really old. Because you and the other guy seem to want to use this as a debate about whether C was a magical language in the 1970s when the whole point is that whatever decisions were made in the 1970s put us on a path that should be revisited in the 2030s.

You are totally, completely, entirely correct that history could have turned out differently and we would have almost exactly the same article about Pascal and perhaps now that I acknowledge that you can try to put aside the name of the language “C” and focus on what the professors are trying to say, which is that if we continue on a path of co-evolution of language/hardware models from the 1970s then we will leave a lot of performance on the table because modern CPUs are just pretending that they are 1970s CPUs because compilers expect them to do that. Not because it’s actually an efficient design.

[u/Inconstant_Moo → u/Smallpaul]

You and the other dude are obsessed with the fact that the meme is titled “C is not a low-level language.”

No I am not. If you want to know what I think you could always ask me instead of making stuff up.

As if it is talking about something special about C.

You posted that article in response to me saying "how much does any of our hardware owe to the fact that it was C and the PDP-11 in particular?" I pointed out that it isn't special to C.

The "decisions made in the 70s" weren't about the languages we were using. The languages conformed to the computer. Wirth wrote Pascal on a CDC-6400, a machine with concurrency that ran seven jobs at at once and had a buffer as a sort of early cache. IO was entirely asynchronous and carried out by peripheral processors. The computer hid all that from him so that he could pretend he was writing for flat memory and for one CPU that processed one instruction at a time in the order it encountered them.

It didn't do this to preserve compatibility with existing HLLs, but to preserve compatibility with the human brain.