I think the knowledge of underlying hardware is useful and good to know.
But also that sort of knowledge got dated pretty quickly in the early computer era. Further, the capabilities of things like optimizing compilers quickly got to a point where they'd outpace most hand written assembly. Today, it's basically just floating point operations where you can still do better than a compiler.
In the early days, you'd have the correct impression that the C compilers spat out utter garbage which was a lot slower than what you could hand craft. As optimization techniques got better and better, the work you did because the compiler was dumb ultimately would have gotten in the way.
I wonder if it's just that kids today (gods that makes me sound old!) are constantly surrounded by entertaining things to do - gaming, TV/films, music, social media.
Some rules are obvious -- cutoff mobiles and pads completely (he doesn't have access to them so it's for me), sit in the library and study from books (I believe this is even possible for programming topics as I can write on paper). Basically, cutting off everything electronics definitely helps -- even putting my phone in the bag improves productivity significantly.
But the problem is, my son is unruly. If I put him in the library, most likely he runs around and messes things up, which ends up we leave early without doing anything.
It's complicated and janky as all get-out, but it made more sense if you were coming from 8080/Z80 development, as this was a scheme to ensure some degree of compatibility with 16-bit 8080 addressing while providing access to much more memory. 8086 was not binary compatible with 8080, but was designed so that 8080 programs could be machine converted to 8086 ones.
In languages like C, this took the form of three different types of pointers: NEAR, FAR, and HUGE. NEAR pointers were 16-bit offsets only, and dereferenced with respect to the current segment (usually in DS). FAR pointers were full segment:offset pairs but pointer arithmetic was only done on the offset which meant objects could be 64K max. HUGE pointers allowed for objects larger than 64k but at a significant performance cost.
Even with 32bit systems where you’d want more than 4GB RAM, application software still had 32 bit addresses (and thus 4GB memory limit).
I think it was a lot more common for 8bit systems to allow for 16 bit addressing though.
It’s been a while though. So hopefully I’m not misremembering things.
The 6502 and Z80 could use 16 bit addressing to access up to 64kb of memory. The 6502 had various other addressing systems, including iirc 8 bits, but none of them were wider tha 16 bits.
8-bit microprocessors used 16-bit addresses.
Similarly, while locking and unlocking memory blocks is no longer generally a concern, most programs still deal with files, and graphics programs still have to call map/unmap functions to access graphics data. All the same tools apply -- helper functions/libraries, RAII, and leak/sanitizer tools to dynamically detect usage errors.
Game consoles like NES, SNES and Game Boy had additional hardware built in the cartridge to support memory mapping/bank switching.
For PCs, EMS (memory) provided a similar concept. It reserved a 64 kB window divided in 16 kB pages in the first 1 MB and allowed to map up to 32 MB.
For me it is fascinating how today I can learn a foreign language, or how to code by interacting with the LLM.
What all of these languages have in common is that you can write meaningful programs entirely without pointers or manual memory management. In particular, all of these languages handle strings in a natural, high-level way (treating them as a value) and don't require you to allocate and free buffers for them. Perl goes a step further with arrays and hashmaps and employs a full garbage collector.
I have vague memories of trying C for the first time and getting completely lost and bogged down by all the pointers and memory management. My reaction was the same as yours: how does anyone program in this. Why bother with this complexity when you can just use Pascal where you simply don't have to.
Of course, the Pascal compiler was likely written in C or assembly and all the memory management still had to happen even if it was hidden away from me. To some people, this might mean that I “lost” something, but to me, it meant greater freedom as I was able to explore the world of higher-level programming which I found interesting, and not have to bother with the low-level details which I found tedious and even infuriating.
It biased your selection of data structures and algorithms.
Max 64KB array size meant pointers to allocated structs and linked lists were much more popular back then versus 1 large array of structs.
The Win16 HANDLE memory allocation also meant you had to worry about how you handle structs which had pointers to others structs (a FAR ptr may not be a stable value, unless you locked the HANDLE for the duration of the allocation)
Then you had to worry about stuff that no college programming book talked about (ignore the lack of error checking):
char FAR *p;
char FAR *mem = farmalloc(65536);
for (p = &mem[65535]; p >= &mem[0]; p--) {
dostuff(p);
}
char FAR *p;
char FAR *mem = farmalloc(65536);
for (p = &mem[65535]; p >= &mem[0]; p--) {
dostuff(p);
}
To be fair to Windows, good C courses should still teach this, but I'm not sure if they do :-)
It's UB to set a pointer to before the first element of an array, or after the last element plus one. So, if it knows the call to farmalloc/malloc returns the start of an object, a modern C compiler on a modern architecture may, in principle, optimise the above to an infinite loop.
I've seen something similar on architectures (long ago) where a zero-bit-pattern pointer was a valid memory address you might actually access. Of course p-1 is not less than p when p is zero.
In fact, I’d argue it was more fun than programming Javascript these days.
Petzold's Programming Windows book, for example, devoted an entire chapter (chapter 7) to memory management, with diagrams and examples. In the 2nd edition (which I just pulled off the shelf to check) that chapter runs to some 40 pages.
https://news.ycombinator.com/item?id=48424862
I'll just stop posting on HN.
A submission to survive most likely needs some initial push from non-organic voting.
It probably helps if you share you submission early with your colleagues and in other sites.
[0]Made an AppleTalk chat client/server https://github.com/kalleboo/GlobalTalk-Chat
[1]The equivalent to HeapWalker I used was Metroweks ZoneRanger which was bundled with their compiler. It has a nice visualization of how fragmented the memory is https://bitbang.social/@kalleboo/116302075194704555
The differences were (a) that DOS+Windows was designed so that the same programs could run in both real mode, with overlaying, and 286 protected mode, with segmented virtual memory; and (b) that to really save on RAM DOS+Windows had ideas such as the data segments for DLLs being globally shared across all processes. These added all of the complications mentioned in the headlined article and more besides. It was the operating system, not the processor architecture.
The 68k didn't come with an MMU like the 286 so MacOS couldn't rely on virtual memory like OS/2 did but at least the flat memory space meant you didn't have to juggle 64k segments
Later in the operating system's lifecycle, applications typically used a single code segment and a custom loader to apply relocations, allowing them to use JSR within that segment.
IMHO one of the best design decisions they made; the Unix dynamic linking model seems absolutely like an absurd workaround in comparison.
Also, no mention of FixDS? https://www.geary.com/fixds.html
What? It's just like static linking! Only, you know, we do it at load time. At least the filenames of the shared objects to load are included into the executable — we could instead just load and search the whole of /usr/lib in unspecified order, you know!
One day I was encouraged to write a Windows Sockets emulation layer for ordinary dial-up shell accounts like those offered by netcom. The idea was to allow the use of the recently released Mosaic browser without an actual internet connection. I figured sure, no problem. I'll use curl or some other tool in the shell account to do the actual fetching of URLs, transfer styles over zmodem, and simulate all the tcp/ip calls in the DLL.
I couldn't even get started. The reason is that I couldn't understand how the different Windows applications could all share memory allocated at runtime in the winsock.dll.
I asked a highly experienced ex Microsoft person, and he just said what are you talking about. There's no API to allocate shared memory.
So I gave up. 6 months later someone else did it.
Around then I realized the truth: Windows 3.1 had no memory protection at all. Specifically all global variables in DLLs were shared by default. The hard part wasn't sharing memory among users of a DLL. If anything, the hard part was having good discipline to avoid sharing it.
Since I'd only used multiuser Unix in school, and I knew Windows supported multitasking (even if only the cooperative kind), I just couldn't wrap my head around the idea that I'm multitasking operating system could exist without memory protection.
All of the below is... IIRC
Win16, even in protected mode, in general didn't unless you opted out of the shared VDM. This was to preserve compatibility with how non-protected mode code worked. That said 32bit code or code that specifically marked itself as protected mode got it's own memory space.
> I just couldn't wrap my head around the idea that I'm multitasking operating system could exist without memory protection
NGL... I was shocked when I found out that MacOS before 10... really didn't have much protections at all.
Now in regards to DLLs it all depended on which memory segments were being used, and the respective code on DllMain in regards to the thread/process attachment code and related handles.
Knowing what to search for quickly gave me this article from back in the day,
https://learn.microsoft.com/en-us/archive/msdn-magazine/2000...
Win16 programming was an important formative phase in my career. There is a lot of wisdom in old solutions to thorny problems and knowing them often clues you to how one may adapt them to today's problem. For example, when CPU+GPU programming appeared i immediately imagined CPU memory accessed with "near" pointers and GPU memory accessed with "far" pointers with a switch to a pseudo-segment register.
It also conditioned a programmer to learn about various complexities involved and be careful in their programming i.e. it taught you discipline. You understood your compiler, OS and hardware better and how to write code keeping them all in mind. For example, i often say my study of embedded programming started with Win16!
Another bit of cleverness was "Thunking" between 16-bit and 32-bit code. Here is Raymond Chen on how it worked there and Why can’t you thunk between 32-bit and 64-bit Windows? - https://devblogs.microsoft.com/oldnewthing/20081020-00/?p=20...
When I wrote a binary translator, I ended up having to keep a translated return stack to optimize RET opcodes. That put me in exactly the same position as the Win16 kernel with regard to having to patch pointers (in case of Win16, just the segment part) on stack.
Of course I did not have the benefit of my guests calling a lock function, so I ended up having to run a garbage collection operation to determine which pointers are in use & take exceptions on now-invalidated segments. Lots of extra work that Windows didn't need: it's nice to be king :-)
This was the magic moment for me, learning Windows 3.0 programming. The idea that my program is no longer master of it's world, but instead is just something that gets loaded and called by Windows.