low-level

Well, there are at least two low-level ways of determining whether a given number is even or not: 1. if (num%2 == 0) { /* even */ } 2. if ((num&1) == 0) { /* even */ } I consider the second option to be far more elegant and meaningful, and that's the one I usually use. But it is not only a matter of taste; The actual performance may vary: usually the bitwise operations (such as the logial-and here) are far more efficient than a mod (or div) operation. Of course, you may argue that some compilers will be able to optimize it anyway, and I agree...but some won't. Another point is that the second

I know in linux it is as simple as /dev/sda but in Windows how do you open a disk and start reading data at the low level? In python I've tried: f = open("K:", "r") and I get this error: Traceback (most recent call last): File "<stdin>", line 1, in <module> IOError: [Errno 13] Permission denied: 'K:' I get this error even as administrator. From http://support.microsoft.com/kb/100027 To open a physical hard drive for direct disk access (raw I/O) in a Win32-based application, use a device name of the form \\.\PhysicalDriveN where N is 0, 1, 2, and so forth, representing each of the physical

Anyone knows of a sensible way to create an ARBITRARY sound wave in C# and play it back from the speakers? This issue has been coming back to every now and then for years, I always end up giving it up after a lot of failure without finding a solution. What I want to do is like a reverse-visualizer, that is, I don't want to generate "numbers" from sound, I want to generate sound from numbers. Like get a function that I provide with sample rate, sample size, and the sound data (an array of integers for example), and it would generate the appropriate wav file from it (real-time sound playback

I don't want to optimize anything, I swear, I just want to ask this question out of curiosity. I know that on most hardware there's an assembly command of bit-shift (e.g. shl , shr ), which is a single command. But does it matter (nanosecond-wise, or CPU-tact-wise) how many bits you shift. In other words, is either of the following faster on any CPU? x << 1; and x << 10; And please don't hate me for this question. :) Potentially depends on the CPU. However, all modern CPUs (x86, ARM) use a "barrel shifter" -- a hardware module specifically designed to perform arbitrary shifts in constant time.

I'd like to experiment using the Raspberry Pi for some different low level embedded applications. The only problem is that, unlike the AVR and PIC microcontroller boards available, Raspberry Pi typically runs an OS (like Raspbian) that distributes CPU time across all running programs and makes it impractical for certain real time applications. I've recently learned that, assuming you have a bootloader like GRUB installed, running a C program on x86 (in the form of a kernel) takes very little actual setup, just an assembly program to call the main function and the actual C code. Is there a way

I'm really wanting to learn assembly. I'm pretty good at c/c++, but want a better understanding of what's going on at a lower level. I realize that assembly related questions have been asked before, but I'm just looking for some direction that's particular to my situation: I'm running windows 7, and am confused about how I should start working with assembly. Do I have to start with x64 because I'm running windows 7? Some people have said 'start with 32 bit first' - how do I go about doing this? What does my operating system have to do with my ability to write assembly for '32' or '64' bit. In

Inspired by this question How can I force GDB to disassemble? I wondered about the INT 21h as a concept. Now, I have some very rusty knowledge of the internals, but not so many details. I remember that in C64 you had regular Interrupts and Non Maskable Interrupts, but my knowledge stops here. Could you please give me some clue ? Is it a DOS related strategy ? From here : A multipurpose DOS interrupt used for various functions including reading the keyboard and writing to the console and printer. It was also used to read and write disks using the earlier File Control Block (FCB) method. DOS can