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Imagine you are interviewing a developer and find this line in his/her CV: Personal achivement: - I built my own OS and C compiler Looks really impressive tod

by anta40 6y ago

Imagine you are interviewing a developer and find this line in his/her CV: Personal achivement: - I built my own OS and C compiler Looks really impressive today, but perhaps it was the norm 3 or 4 decads ago. Anyway, I envy such people who can do that. Let me try that once again.... :)

bombcar 6y ago
It’s a feat - but do remember that a simple OS and a simple compiler are NOT the beasts we think of today. DOS for example is not much more than a standard library- and early UNIX wasn’t much more.
- haolez 6y ago
  The first version of DOS had a filesystem that didn't support directories! :)
  - prox 6y ago
    It will never catch on! :)
    - bombcar 6y ago
      We laugh but iOS didn’t really support “files and directories” until quite recently.
      - orhmeh09 6y ago
        iOS, being a Unix, has always supported files and directories in full. It wouldn’t be able to work otherwise.
        pjmlp 6y ago
        It doesn't matter, when they aren't surfaced that way to the user.
        macintux 6y ago
        That’s like saying ignition doesn’t matter for an internal combustion engine because it isn’t surfaced to the user.
        pjmlp 6y ago
        Indeed, that is why cars are changing to electric and for the user the driving experience is mostly unchanged.
        zepto 6y ago
        > ignition doesn’t matter for an internal combustion engine You said ‘indeed’ which makes it look like you are saying this is true? I think you may be confusing the ignition switch or key, with the ignition of fuel in the engine. The ignition of fuel is absolutely necessary for internal combustion engines, just as a full file system was always necessary for iOS.
        pjmlp 6y ago
        Except a car doesn't need a combustion engine to fullfil its purpose, electric engines don't have combustion. There is nothing on the iOS experience that requires a file system with POSIX semantics. In fact that isn't what app developers using directly, rather Objective-C and Swift abstractions of a file system.
        zepto 6y ago
        > Except a car doesn't need a combustion engine to fullfil its purpose, electric engines don't have combustion. This is true, and is why using it as an analogy doesn’t work. > There is nothing on the iOS experience that requires a file system with POSIX semantics. Nobody mentioned posix before now. This is moving the goalposts. > In fact that isn't what app developers using directly, rather Objective-C and Swift abstractions of a file system. This is not true. iOS provides all levels of Unix file system access from posix and libc upwards. Many apps and libraries make use of lower level access than Swift and Obj-C apis. In addition, even those abstractions won’t work without a file system. They depend on concepts like files and directories. This is why iOS had to have one when it shipped, and why a car power train is not a valid analogy.
marcodiego 6y ago
> Personal achivement: - I built my own OS and C compiler And computer.
- java-man 6y ago
  me too. 8080A with three power rails!
necubi 6y ago
Doing this today is actually way, way easier than it would have been back then. Today we have a wealth of information and much better tooling (QEMU alone makes the process of writing an OS so much easier). Writing a simple OS and compiler are both common school projects, so many programmers today have done it.
- jdsully 6y ago
  It's easier in some ways but harder in a lot of others. For starters the definition of an "OS" has greatly expanded over time. In the CP/M and even DOS days it was a very primitive shell and some disk I/O routines. Secondly low level knowledge was a lot more common because you needed it to get anything done. You could do some interesting things in BASIC but "real" programs were written in assembly.
  - 082349872349872 6y ago
    Compare cooking dinner while backpacking vs cooking dinner at home: both produce warm food, but we probably neither take an induction stove (or microwave!) backpacking, nor build campfires in a kitchen.
- buffet_overflow 6y ago
  Agreed, I had a similar takeaway. >...faded lineprinter paper show that the bulk of the work on OMU dates from March/April/May 1984... by mid 1984 I had a perfectly usable O/S It's impressive that Hosgood made what he did when he did. It's equally impressive for an entirely different set of reasons that modern CS students can burn through that in a semester. Or you could look it up on WikiHow.
LeonM 6y ago
As an electrical engineering student I designed and build my own processor (in VHDL), and wrote a simple assembler for it, it's not that difficult, just tedious. Eventually I added a VGA frame buffer, PS/2 keyboard module and RS-232 support and made it work as a terminal. By connecting 2 of these 'computers' with a null-modem cable, we would have a little chat-box application to display during open days at my university. Ironically, I was once rejected for a programming job because I studied electronics, not computers. So clearly I didn't know how computers worked.

by anta40 6y ago

bombcar 6y ago

It’s a feat - but do remember that a simple OS and a simple compiler are NOT the beasts we think of today. DOS for example is not much more than a standard library- and early UNIX wasn’t much more.

haolez 6y ago
The first version of DOS had a filesystem that didn't support directories! :)
- prox 6y ago
  It will never catch on! :)
  - bombcar 6y ago
    We laugh but iOS didn’t really support “files and directories” until quite recently.
    - orhmeh09 6y ago
      iOS, being a Unix, has always supported files and directories in full. It wouldn’t be able to work otherwise.
      - pjmlp 6y ago
        It doesn't matter, when they aren't surfaced that way to the user.
        macintux 6y ago
        That’s like saying ignition doesn’t matter for an internal combustion engine because it isn’t surfaced to the user.
        pjmlp 6y ago
        Indeed, that is why cars are changing to electric and for the user the driving experience is mostly unchanged.
        zepto 6y ago
        > ignition doesn’t matter for an internal combustion engine You said ‘indeed’ which makes it look like you are saying this is true? I think you may be confusing the ignition switch or key, with the ignition of fuel in the engine. The ignition of fuel is absolutely necessary for internal combustion engines, just as a full file system was always necessary for iOS.
        pjmlp 6y ago
        Except a car doesn't need a combustion engine to fullfil its purpose, electric engines don't have combustion. There is nothing on the iOS experience that requires a file system with POSIX semantics. In fact that isn't what app developers using directly, rather Objective-C and Swift abstractions of a file system.
        zepto 6y ago
        > Except a car doesn't need a combustion engine to fullfil its purpose, electric engines don't have combustion. This is true, and is why using it as an analogy doesn’t work. > There is nothing on the iOS experience that requires a file system with POSIX semantics. Nobody mentioned posix before now. This is moving the goalposts. > In fact that isn't what app developers using directly, rather Objective-C and Swift abstractions of a file system. This is not true. iOS provides all levels of Unix file system access from posix and libc upwards. Many apps and libraries make use of lower level access than Swift and Obj-C apis. In addition, even those abstractions won’t work without a file system. They depend on concepts like files and directories. This is why iOS had to have one when it shipped, and why a car power train is not a valid analogy.

marcodiego 6y ago

> Personal achivement: - I built my own OS and C compiler And computer.

java-man 6y ago
me too. 8080A with three power rails!

necubi 6y ago

Doing this today is actually way, way easier than it would have been back then. Today we have a wealth of information and much better tooling (QEMU alone makes the process of writing an OS so much easier). Writing a simple OS and compiler are both common school projects, so many programmers today have done it.

jdsully 6y ago
It's easier in some ways but harder in a lot of others. For starters the definition of an "OS" has greatly expanded over time. In the CP/M and even DOS days it was a very primitive shell and some disk I/O routines. Secondly low level knowledge was a lot more common because you needed it to get anything done. You could do some interesting things in BASIC but "real" programs were written in assembly.
- 082349872349872 6y ago
  Compare cooking dinner while backpacking vs cooking dinner at home: both produce warm food, but we probably neither take an induction stove (or microwave!) backpacking, nor build campfires in a kitchen.
buffet_overflow 6y ago
Agreed, I had a similar takeaway. >...faded lineprinter paper show that the bulk of the work on OMU dates from March/April/May 1984... by mid 1984 I had a perfectly usable O/S It's impressive that Hosgood made what he did when he did. It's equally impressive for an entirely different set of reasons that modern CS students can burn through that in a semester. Or you could look it up on WikiHow.

LeonM 6y ago

As an electrical engineering student I designed and build my own processor (in VHDL), and wrote a simple assembler for it, it's not that difficult, just tedious. Eventually I added a VGA frame buffer, PS/2 keyboard module and RS-232 support and made it work as a terminal. By connecting 2 of these 'computers' with a null-modem cable, we would have a little chat-box application to display during open days at my university. Ironically, I was once rejected for a programming job because I studied electronics, not computers. So clearly I didn't know how computers worked.