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OS Development

nick123

     I've been studying assembly language for a long long long time, and I want to try OS Development. I've heard of MikeOS it was entirely written in real mode assembly. I looked over the code of MikeOS and now I feel very discouraged. It is a lot of complicated code just for a simple os.

 

MikeOS - simple x86 assembly language operating system

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  • 0

    Most OS are not written in assembler but in C or other high level language.

    To write even a small scheduler type OS in assembler is an odd thing to do since it will make it take longer and it won't be portable.

    However you sometimes have to write small sections of the code in assembler because there may be things that C (or other high level language) just can't do - like, for example atomic compare and set or re-entrant interrupts on an arm.

    Sometimes you need to use assembler because even optimizing compilers just don't get it - so you might design a filter where the coefficients and processing steps are carefully arranged so that you end up with all division being by 2^8 or 2^16 but the compiler doesn't see it (much less common than it used to be) so you end up using assembler to get the ultimate performance. But you should always write the code in straightforward C first and only hand optimize in assembler if the compiled code isn't fast enough. (This is very unlikely to be the case with a boot loader.)

     

    If you are using tiny 8 or 4 bit processors then you may have no choice but to use assembler, but make sure you are going to use a lot of them else it will be cheaper to use an ARM Cortex M0 and write the code in C with much less time and effort.

     

    MK

  • 0 in reply to michaelkellett

    Arduino comes to mind when you say too slow to process interrupts on a large scale per second.

    Clem

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  • 0 in reply to clem57

    Well the Arduino is a bit of a mad thing - running a C/C++ hybrid on an 8 bit processor and competing in a 32bit world the amazing thing is that it holds its own so well. It has problems during interrupts since it has to stack 16 bit (or more) context over an 8 bit bus so needs extra cycles.

     

    I used to use AtmelAVRs quite a bit but I haven't designed one into a new project for several years (about 7, I think).

     

    MK