4 ms·

Nice article. I grew up when it wasn't really possible to be into computers and not have a visceral sense of this. Presumably nowadays it would be possible to g

Nice article. I grew up when it wasn't really possible to be into computers and not have a visceral sense of this. Presumably nowadays it would be possible to get very far into programming (maybe into a career in it!) without practically encountering storage-as-bunch-of-bits, although surely people know that's what's there.

JohnFen 3y ago
> it would be possible to get very far into programming (maybe into a career in it!) without practically encountering storage-as-bunch-of-bits I increasingly meet devs who have no such knowledge (beyond a vague understanding). They sometimes don't even understand bitwise operations or when to use them and why. It completely boggles my mind.
- gumby 3y ago
  I really hoped for the democratization of programming and now it's happened I sometimes have a WTF like that. But there's still a lot of call for programmers who understand the hardware and/or low-level protocols. We write the stuff the other people use to get their work done.
  - JohnFen 3y ago
    Oh, I agree. I don't think such devs are lesser in some way. They're just working at a high enough level of abstraction that such things aren't that relevant to what they're doing. The old fart in me does struggle to understand how people can learn to be devs without learning bit-level stuff, but that's just me noticing the strange new ways of a strange new world. And for devs like myself, who are happiest when working close to the metal, it's a professional advantage. As the pool of devs who know how to (and enjoy) twiddle bits shrinks, those of us who are left have more work and can command higher pay rates. The software industry is maturing and, like other industries that have matured, the people in it are increasingly specialists. My bit-twiddling ways are just a different specialty.
    - _1rth 3y ago
      I'm one of those new programmers. I'll sometimes do low level dev, but I don't use bitwise operations much. I guess I just don't recognise where they're useful. I'm always a bit awed when people chain a few for massive speedups. How can I learn?
      - gumby 3y ago
        Read a lot of code and work with someone who does that kind of thing. Also you might want to brush up on math and algos: a lot of this "skill" is really just thinking about what the actual computation is. And that just comes from experience.
        JohnFen 3y ago
        Heh, that is probably more useful advice than the freaking essay I wrote in response.
        dmvdoug 3y ago
        False. Your freaking essay was a great read for me. But I’m not a developer/programmer, just a very interested outsider.
      - JohnFen 3y ago
        I've been doing this from well before the internet was a thing, so I'm not actually familiar with good online resources to help. But I can give very general search suggestions. I tend to think of there being two classes of problems that are addressed at the bitwise level. The first is optimization and the second is hardware control. The techniques the two use are rather different. Optimization is a tricky topic, because you can't always get great gains there though bitwise operations, but when you can, the gains can be huge. This is because (for compiled languages) modern compilers tend to be very good at this sort of optimization and will do things in very efficient way to begin with. You taking the bits into your own hands aren't likely to improve on them. Also, there are processors where certain optimizations don't apply. For example, shifting a value one bit to the left is the same as multiplying by 2, and to the right is the same as dividing by 2. In many processors, the bit shift is much faster than the multiplication operation, so there's a win to be had there. In others, however, there is not such a huge speed difference. It all depends. In terms of hardware control, what you want to know is more obvious: what is the most efficient way to work with single or small groups of bits? What's the fastest way to count bits? That sort of thing. As an aside -- where I currently work, one of the interview problems is to have the applicant write code that counts how many bits are set in a word. Even high-level programmers will generally know how to do this -- but the method they use tells you a lot about the focus of their training and skillset. Bonus points if you can say why this is a useful thing to do, and what the Big O for your method is. In any case, I would suggest reading up on Boolean algebra to start to get a handle on this stuff. If you want to really wow people (at least ones who aren't graybeards), then a fun trick is to learn to model things (system states, whatever) as boolean networks (linking together AND, OR, XOR, etc. "gates" that result in a desired truth table), then use Karnaugh maps to reduce the network to the smallest possible number of components. I learned this as a way of reducing component counts in digital logic circuits, but I still find use for them to this day in purely software applications and often get called a wizard for being able to produce complex decision-making code that is very fast. The price you pay, of course, is that such code is not easy to follow for the poor souls who have to work with it later.
toast0 3y ago
It certainly is; my interview problem deals with bytes and optionally bits and I can't assume candidates have any knowledge of things at that level, because a lot of candidates don't. Kind of weird, IMHO, but not really a big deal, they can treat bytes as abstract constructs for the most part and go through the question well enough to show me if they can understand a problem described in words, figure out an output format and calculate example output given example input, and then write a program that does what they said it would do. The details of how bytes work can be explained on the way as needed.
vba616 3y ago
>I grew up when it wasn't really possible to be into computers and not have a visceral sense of this "A disk is a bunch of bits" doesn't seem to me like an accurate characterization of microcomputers at any time, really, in the last 50 years. I started to say that I think things got really complicated with SSDs, but spinning hard and floppy disks were never that simple either. I don't mean to nitpick, and I'm no expert, but I think the non-bit-array nature of storage had a lot of implications for users doing low level stuff - for example, copy protection sometimes exploited the hardware to try to make an uncopyable disc. Or if you were setting up partitions on a hard drive, you'd need to know about more than just "disk = bits". https://en.wikipedia.org/wiki/Cylinder-head-sector https://en.wikipedia.org/wiki/Cylinder-head-sector https://en.wikipedia.org/wiki/Logical_block_addressing https://en.wikipedia.org/wiki/Logical_block_addressing https://en.wikipedia.org/wiki/Modified_frequency_modulation https://en.wikipedia.org/wiki/Modified_frequency_modulation "Commodore's Amiga used an unusual format which got closer to the disk's raw (unformatted) capacity by eliminating the gaps between sectors and simplifying the identification data. This meant that individual sectors could not be rewritten; the Amiga would simply rewrite the entire track." https://en.wikipedia.org/wiki/Floppy_disk_format https://en.wikipedia.org/wiki/Floppy_disk_format I also remember that audio CDs, even though you could read them on a computer, were very, very much not bit arrays. Despite their vaunted "digital" nature, you couldn't rely on getting the same bitstream every time if you were ripping them to disk. https://en.wikipedia.org/wiki/Cdparanoia https://en.wikipedia.org/wiki/Cdparanoia

JohnFen 3y ago

> it would be possible to get very far into programming (maybe into a career in it!) without practically encountering storage-as-bunch-of-bits I increasingly meet devs who have no such knowledge (beyond a vague understanding). They sometimes don't even understand bitwise operations or when to use them and why. It completely boggles my mind.

gumby 3y ago
I really hoped for the democratization of programming and now it's happened I sometimes have a WTF like that. But there's still a lot of call for programmers who understand the hardware and/or low-level protocols. We write the stuff the other people use to get their work done.
- JohnFen 3y ago
  Oh, I agree. I don't think such devs are lesser in some way. They're just working at a high enough level of abstraction that such things aren't that relevant to what they're doing. The old fart in me does struggle to understand how people can learn to be devs without learning bit-level stuff, but that's just me noticing the strange new ways of a strange new world. And for devs like myself, who are happiest when working close to the metal, it's a professional advantage. As the pool of devs who know how to (and enjoy) twiddle bits shrinks, those of us who are left have more work and can command higher pay rates. The software industry is maturing and, like other industries that have matured, the people in it are increasingly specialists. My bit-twiddling ways are just a different specialty.
  - _1rth 3y ago
    I'm one of those new programmers. I'll sometimes do low level dev, but I don't use bitwise operations much. I guess I just don't recognise where they're useful. I'm always a bit awed when people chain a few for massive speedups. How can I learn?
    - gumby 3y ago
      Read a lot of code and work with someone who does that kind of thing. Also you might want to brush up on math and algos: a lot of this "skill" is really just thinking about what the actual computation is. And that just comes from experience.
      - JohnFen 3y ago
        Heh, that is probably more useful advice than the freaking essay I wrote in response.
        dmvdoug 3y ago
        False. Your freaking essay was a great read for me. But I’m not a developer/programmer, just a very interested outsider.
    - JohnFen 3y ago
      I've been doing this from well before the internet was a thing, so I'm not actually familiar with good online resources to help. But I can give very general search suggestions. I tend to think of there being two classes of problems that are addressed at the bitwise level. The first is optimization and the second is hardware control. The techniques the two use are rather different. Optimization is a tricky topic, because you can't always get great gains there though bitwise operations, but when you can, the gains can be huge. This is because (for compiled languages) modern compilers tend to be very good at this sort of optimization and will do things in very efficient way to begin with. You taking the bits into your own hands aren't likely to improve on them. Also, there are processors where certain optimizations don't apply. For example, shifting a value one bit to the left is the same as multiplying by 2, and to the right is the same as dividing by 2. In many processors, the bit shift is much faster than the multiplication operation, so there's a win to be had there. In others, however, there is not such a huge speed difference. It all depends. In terms of hardware control, what you want to know is more obvious: what is the most efficient way to work with single or small groups of bits? What's the fastest way to count bits? That sort of thing. As an aside -- where I currently work, one of the interview problems is to have the applicant write code that counts how many bits are set in a word. Even high-level programmers will generally know how to do this -- but the method they use tells you a lot about the focus of their training and skillset. Bonus points if you can say why this is a useful thing to do, and what the Big O for your method is. In any case, I would suggest reading up on Boolean algebra to start to get a handle on this stuff. If you want to really wow people (at least ones who aren't graybeards), then a fun trick is to learn to model things (system states, whatever) as boolean networks (linking together AND, OR, XOR, etc. "gates" that result in a desired truth table), then use Karnaugh maps to reduce the network to the smallest possible number of components. I learned this as a way of reducing component counts in digital logic circuits, but I still find use for them to this day in purely software applications and often get called a wizard for being able to produce complex decision-making code that is very fast. The price you pay, of course, is that such code is not easy to follow for the poor souls who have to work with it later.

toast0 3y ago

It certainly is; my interview problem deals with bytes and optionally bits and I can't assume candidates have any knowledge of things at that level, because a lot of candidates don't. Kind of weird, IMHO, but not really a big deal, they can treat bytes as abstract constructs for the most part and go through the question well enough to show me if they can understand a problem described in words, figure out an output format and calculate example output given example input, and then write a program that does what they said it would do. The details of how bytes work can be explained on the way as needed.

vba616 3y ago

>I grew up when it wasn't really possible to be into computers and not have a visceral sense of this "A disk is a bunch of bits" doesn't seem to me like an accurate characterization of microcomputers at any time, really, in the last 50 years. I started to say that I think things got really complicated with SSDs, but spinning hard and floppy disks were never that simple either. I don't mean to nitpick, and I'm no expert, but I think the non-bit-array nature of storage had a lot of implications for users doing low level stuff - for example, copy protection sometimes exploited the hardware to try to make an uncopyable disc. Or if you were setting up partitions on a hard drive, you'd need to know about more than just "disk = bits". https://en.wikipedia.org/wiki/Cylinder-head-sector https://en.wikipedia.org/wiki/Cylinder-head-sector https://en.wikipedia.org/wiki/Logical_block_addressing https://en.wikipedia.org/wiki/Logical_block_addressing https://en.wikipedia.org/wiki/Modified_frequency_modulation https://en.wikipedia.org/wiki/Modified_frequency_modulation "Commodore's Amiga used an unusual format which got closer to the disk's raw (unformatted) capacity by eliminating the gaps between sectors and simplifying the identification data. This meant that individual sectors could not be rewritten; the Amiga would simply rewrite the entire track." https://en.wikipedia.org/wiki/Floppy_disk_format https://en.wikipedia.org/wiki/Floppy_disk_format I also remember that audio CDs, even though you could read them on a computer, were very, very much not bit arrays. Despite their vaunted "digital" nature, you couldn't rely on getting the same bitstream every time if you were ripping them to disk. https://en.wikipedia.org/wiki/Cdparanoia https://en.wikipedia.org/wiki/Cdparanoia