Author Archives: dmytrish

Brave new world of tablet computing

The last two weeks were a time of revelations for me: I dropped off the stream of IT news and focused on math and lectures much more than before, time to time arguing with my university lectors. They seem to live in the computer world of late 90s (it’s Ukraine, yeah): they still moan about “redundant” gigaherzs and processor cores, about unnecessary Windows (lolwhut, who use it nowadays?) features put together by malevolent software vendors intentionally in order to get us use new hardware and so on (for me having been exposed to HN crowd for some time, this is pretty ridiculous).

One of the most outrageous claims was that “8 cores are enough for anything, increasing the amount won’t gain anything”. My first reaction was “lol, do you still live in the world of the single-core?!”, I tried to argue that “Modern systems have hundreds of threads running in parallel, wouldn’t it be nice for each of them to have a core?”, but this had been easily refuted: “Are they doing anything most of the time?” – and I had to agree that most of the time they’re blocked by some kind of IO (even now on my Core i7 8-core CPU I see only two tasks running). So I proceeded: “Yes, you are right, those computing resources are not required for the mundane user activities. And the market reflects this: it steadily diversifies, non-fastidious users moving to tablets, gamers and professionals using the desktop for the work and so on”. I felt proud: I had been bringing a new vision to those old-school people.

Then I was discussing my programming projects with my peer, showing it on my Nexus 7 on Github (my laptop broke recently, so I am forced to use the tablet), I’d shown Terminal IDE, c4droid, Limbo PC emulator with Kolibri OS and my own COSEC inside. The feeling was: it’s so much of a toy, not a real productive environment, it can so much and still is very far from good enough to do anything creative. I returned home and read news: Intel abandons the motherboard manufacturing, Dell shows an “office” tablet.

The brave new world of tablet computing is awfully hostile to usual programmer’s activities (keyboard, the old clunky mechanical keyboard with mechanical buttons, I really, really miss you on slick modern gadgets): do you want to write a program? You have to go through the pain of software keyboard (even if it’s Hacker’s keyboard), you have to do programming inside a separate application, without hope to do something system-wide until it’s packed into APK and installed (coming from Linux, where programs breath with cooperation and gluing together, Android apps are a bunch of black boxes, each on its own), you have to sign every program in order to comply with the wallen garden rules, you can’t install another operating system to your gadget easily (free bootloaders anyone?) – it seems that the brave new world of tablets does everything to make hacking and fiddling around more complicated and hindered.

The problem is: how will the new generation of hackers emerge? How to support the desire to know what’s inside of complex systems (be it hardware or software) for a generation that will not have seen a desktop computer? How to grow the ability to tinker about? How to save it from suffocation in the world of fences and locks?

Haskell OpenGL animation done right: using closures and channels instead of IORef’s

There is a lot of Haskell OpenGL tutorials on the web introducing to basic OpenGL drawing in Haskell. I’ve read about a dozen of them, but none are highlighting an important issue right: how to react to user’s input? The tutorials either omit this topic, or fall back to ugly and non-idiomatic IORefs to return data from callbacks (even the Haskell wiki goes this way). Although there is a much nicer way to handle GLUT/GLFW callbacks which is explained below.

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COSEC: six months

This spring my assembly coding experiments grew to something more: I moved from the x86 real mode to first steps in the protected mode environment, which seemed hostile and quite unusual. A lot of intricate and arcane assembly code needed to fit opportunities of a full 32bit mode really puzzled me first, but my slow progress was persistent enough to run first C code examples and to see a “Hello world” message in an OSless emulator.

I’ve been really impressed by Linux and its kernel and, like a child, wanted to know “how does this thing work”, so writing a linux-like kernel was a pleasant and useful challenge for my programming skills. My guidelines are not fancy: system clearness and simplicity, minimal POSIX-compatibility and experiments inspired by Plan 9 from Bell Labs, like network transparency and resources unification through files. Also I lean to microkernel design as far as it does not complicate the picture.

I haven’t had a definite goal of my project for a long time, I fluctuated between considering this OS just a training ground for system programming and exaggerated expectations for a new OS architecture and language-based features (resembling Singularity software stack), although my experience in writing code for managed platforms and writing interpreters/virtual machines itselves is miserable (and this is my first large project in pure C). Now I came to a definite goal: I want to have a minimal self-hosting POSIX-like OS using C (roughly corresponding to Linux 0.01 functionality, but a bit more slim, there are two decades of history after Linux creation).

Now my system is still quite nascent, but the experiments now involve much more mature things. Now my tiny OS contains:

  • a basic context switching (which is still not used);
  • basic userspace capabilities (and a single system call, SCS_DBG_PRINT, which print a message from userspace);
  • draft of Virtual File System;
  • my own implementation of heap using the firstfit algorithm;
  • implementation of some libc functions.
  • some drivers: keyboard, timers, serial port, PCI probing;

The system is still a single binary with simplest built-in kernel shell (userspace is waiting for FS implementation on order to be able host a functional shell). It is loaded with GRUB according to GNU mutliboot specification, though I have my own bootloader and switch-to-protected-mode code snippets.

Plans for the future are:

  • to add paging and modern-style memory protection;
  • to implement functional VFS and some popular FS drivers like FAT/ext2/iso9660;
  • to make the userspace really work: full-featured process with own address spaces, pipes, sockets;
  • to port Newlib (a C library implementation) and write a system-dependent userspace code for launching bash/gcc/vim on top of it;
  • an ELF loader;
  • to make it cross-platform with ARM support;
  • to start writing a simple network stack (arp, icmp, ip, tcp/udp, telnet/http/ftp);

Here is the source code:

COSEC on Github

In Ukrainian | Українською



I am a programmer from Ukraine. My interests are:

  • low-level, system programming (x86, x86_64, ARM), C and assembly languages for aforementioned platforms;
  • OS theory, design and implementation (but I am not that hardware fan), distributed and managed operating systems;
  • operating systems: Unix of all kinds, especially Linux (now I’m getting familiar with its kernel), Inferno, Plan 9 from Bell Labs; QNX, L4; BeOS, KolibriOS; COSEC (which is written by me);
  • modern (and timeless) script and functional programming languages like Lisp/Scheme and Python (my plans are to get closer to Haskell and OCaml);
  • a bit of natural language processing and practical AI;
  • once upon a time I had some experience with C++ and OpenGL;
If it is not empty words for you, welcome to my blog.