Hidden Files in C64 OS

https://www.c64os.com/post/hiddenfiles

by ingve • 2 years ago

96 25 2 years ago

One way to gauge when I started in computing is that figures like https://s3.amazonaws.com/com.c64os.resources/weblog/hiddenfi... were what our textbook authors felt was really important for us to know, yet I have spent more than 3 decades since with absolutely no need to care about physical disk layout (the closest I ever got was video editing in the early 90s).

At some point Widlar's "Every idiot can count to one" stopped being pejorative and was wholeheartedly embraced by the entire industry.

Has anyone attempted to do a timeline of computing by "what no longer matters" in each decade?

Civilisation advances by extending the number of important operations which we can perform without thinking of them. —ANW

sixothree• 2 years ago

I feel like schools have gotten a lot better about this over the years. Of course students are taught to walk using the rudimentary components when they are learning to program.

We had to write a B-tree implementation in Java when I was in school. I have used that knowledge exactly zero times. But I am betting algorithms are still important.

TillE• 2 years ago

Yeah I got my undergrad CS degree (a good mix of theory and practice) about 20 years ago and I can't think of much that's truly outdated. I certainly don't use Java or MIPS32 assembly or Solaris these days, but that wasn't really the point of those classes.

Even with truly obsolete stuff like the details of hard drive technology, there's something valuable to be learned in examining how people solved problems at the time with the tools they had.

0823498723498723• 2 years ago

The B-tree has at least two lessons, independently of whether you ever re-implement one: (a) using trees instead of flat search gains an O(log n) over O(n) algorithmic factor, and (b) using chunky flat elements sized to the bandwidth-delay product of storage results in significant wall-clock (constant factor?) gains.

I fail to see how CHS provides equivalently valuable lessons? https://news.ycombinator.com/item?id=39826433

FLT8• 2 years ago

I think mechanical sympathy is still useful, even in a world of 'plenty'.. it's people with that kind of understanding who are able to get current day computers to do things that others will have to wait until tomorrow to achieve.

bombcar• 2 years ago

There's something to be said for learning the various effects virtualization layers can have, even if they're not affecting you today.

Something similar will happen again at another level.

corysama• 2 years ago

When I was streaming audio and video in PlayStation 2 games, I had to care a lot about physical disk layout. But, even then it boiled down to: Seek times are huge, sector and cluster sizes are your atomic ops under the hood, inner rings are low-bandwidth-low-variance, outer rings are high-bandwidth-high-variance.

Since then, not so much.

These days with NVMe drives, things are much easier. But, there are still things to keep in mind. I haven't dug deep. But, my impression is: Even though 4K random reads are incredibly faster than they used to be, large (256K-2MB) reads are yet faster still. Maxing out modern drives requires having multiple requests in flight. So, multiple threads or async operations. Modern drives are so fast that the memory copies involved in buffered fread() can add 33ish% overhead. Consider memory-mapped read-only files. Even better: If you have millions of users, you need 1-in-a-million reliability. Consider SQLite or LMDB as alternatives to fwrite().

sunir• 2 years ago

The principle still matters. Learning how underlying storage works helps optimize data layout, write and read for speed.

It’s just that storage has changed. Caches may be important now for instance

userbinator3• 2 years ago

It has changed such that the "traditional" CHS order hasn't been the physical layout of HDDs for probably at least two decades now. Not long ago I posted an article with more details of that: https://news.ycombinator.com/item?id=39428728

emrah• 2 years ago

It's inspiring to watch people work on dead tech with such enthusiasm and energy. I'd love someone to do an AMA and explain how they manage their focus and enthusiasm to keep working on such tech

Solvency2• 2 years ago

Don't have a soul sucking job. Don't have kids. Or a relationship. Endless potential focus. But not everyone has a razor sharp passion.

sneilan12• 2 years ago

The author has children. And a wife. https://www.c64os.com/legal/thanks-and-credits/

userbinator3• 2 years ago

It's not "dead", it's "mature", "stable", or "known". You can build on it and focus on what you want to do without worrying that the foundation will be pulled out from under you.

chrismcb• 2 years ago

Because it is fun. It is challenging, and interesting. And nostalgic.

zengargoyle• 2 years ago

Freshman year of high school I took a class called "Business Computer Applications". It was 1983 and I was 13. We were using Apple II+ computers or their clones. I had an Apple II+ since they came out and knew lots of things by then. I "wowed" my teacher with 3 line programs and such. On our classroom floppy I had a file with a control character in it's name, it was a disk editor. Knowing the disk directory layout things (it was a linked list of blocks), I carved out a whole hidden set of directory entries. So each day of class I would load up the disk editor using the invisible control characters, patch back in my hidden blocks, play with my hidden files, then at the end of class I'd load the disk editor up again and hide my files. Teacher never saw what was really on that disk.

brokenmachine• 2 years ago

classroom floppy

Wow

avidphantasm• 2 years ago

Fantastic write-up. I wish the documentation for all systems was this good.

russfink• 2 years ago

I find it fascinating that the drive hardware manages the filesystem. When did it become that the OS software managed the filesystem, and in the end, which is better?

userbinator3• 2 years ago

When did it become that the OS software managed the filesystem

I think among early computers the C64 drive was somewhat of an exception; in some ways it's more like a NAS than a block device.

myrandomcomment• 2 years ago

This was unique to Commodore. They owned MOS which made the chips so it was not as costly for them to do this. Honestly it sucked longer term because there was no way to really upgrade how the filesystem DOS worked unlike on the Apple or the Atari.

It was cool however because there were tools that offloaded things to the drive CPU. You could also write programs for copying disk that you loaded into the RAM on the drive and then disconnected them from the computer. You used the drive lights to tell you when to swap the disk.

Hidden Files in C64 OS

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