If you had read my other question, you'll know I've spent this weekend putting together a 6502 CPU emulator as a programming exercise. The CPU emulator is mostly complete, and seems to be fairly accurate from my limited testing, however it is running incredibly fast, and I want to throttle it down to the actual clock speed of the machin...
I have this C-code to do multiplications over GF(8): int32_t GaloisMultiply (int32_t a, int32_t b) { int32_t i; int32_t mask = 0x100; int32_t y = 0; for(i=0;i<8;i++) { if(b & mask) { y ^= a; } mask >>= 1; y <<= 1; } if(b & 0x1) { y ^= a; } return(y); } That's more or less the text-boo...
On the MSVC++ compiler, one can use the __int8, __int16, __int32 and similar types for integers with specific sizes. This is extremely useful for applications which need to work with low-level data structures like custom file formats, hardware control data structures and the like. Is there a similar equivalent I can use on the GCC compi...
This is mostly a theoretical question I'm just very curious about. (I'm not trying to do this by coding it myself or anything, I'm not reinventing wheels.) My question is how the uppercase/lowercase table of equivalence works for Unicode. For example, if I had to do this in ASCII, I'd take a character, and if it falls withing the [a-z]...
What win32 calls can be used to detect key press events globally (not just for 1 window, I'd like to get a message EVERY time a key is pressed), from a windows service? ...
[This is for PC/Visual C++ specifically (although any other answers would be quite illuminating :))] How can you tell if a pointer comes from an object in the stack? For example: int g_n = 0; void F() { int *pA = &s_n; ASSERT_IS_POINTER_ON_STACK(pA); int i = 0; int *pB = &i; ASSERT_IS_POINTER_ON_STACK(pB); } so o...
A friend and I are going back and forth with brain-teasers and I have no idea how to solve this one. My assumption is that it's possible with some bitwise operators, but not sure. ...
This is a follow-up to my question yesterday: CMS kindly provided this example of using bitwise operators to add two numbers in C: #include<stdio.h> int add(int x, int y) { int a, b; do { a = x & y; b = x ^ y; x = a << 1; y = b; } while (a); return b; } int main( void ){ printf( "6 ...
Creating an OS seems like a massive project. How would anyone even get started? For example, when I pop Ubuntu into my drive, how can my computer just run it? (This, I guess, is what I'd really like to know.) Or, looking at it from another angle, what is the least amount of bytes that could be on a disk and still be "run" as an OS? ...
Should all decent programmers be expected to know at least something about low-level stuff such as the following: The gist of how garbage collection is implemented, how memory management works without GC, and exactly what the difference is between the heap, the stack and the static data segment? At least be able to read assembly langua...
The C standard library is notoriously poor when it comes to I/O safety. Many functions have buffer overflows (gets, scanf), or can clobber memory if not given proper arguments (scanf), and so on. Every once and awhile, I come across an enterprising hacker who has written his own library that lacks these flaws. What are the best of the...
I'm curious how many cycles it takes to change contexts in Linux. I'm specifically using an E5405 Xeon (x64), but I'd love to see how it compares to other platforms as well. ...
Suppose we have these local variables: int a = 0; int b = 1; int c = 2; int d = 3; As far as I know, these will be allocated on the system stack, like this: | | | 3 | d | 2 | c | 1 | b |_0_| a Does this mean that in order to get the value of a, the values of d, c and b must first be popped out of the stack? If so, where do these ...
I'm not exactly sure how to tag this question or how to write the title... so if anyone has a better idea, please edit it! Here's the deal: Some time ago I had written a little but cruicial part of a computing olympiad management system. The system's job is to get submissions from participants (code files), compile them, run them again...
I'm going to graduate soon in electronics and tlc engineering and I have some decent OO programming experience with PHP and Java. Now I would like to try starting a career as a C programmer. I'm interested in C since this is, I think, the most suited language, without considering Assembly, to develop device drivers, firmwares and other l...
I am interested in writing a very minimalistic compiler. I want to write a small piece of software (in C/C++) that fulfills the following criteria: output in ELF format (*nix) input is a single textfile C-like grammar and syntax no linker no preprocessor very small (max. 1-2 KLOC) Language features: native data types: char, int an...
I know that screen readers and similar software exists to help the blind and visually impaired to use computers when in Windows or other operating systems. I am curious as to what support is available in lower level environments such as OS installers and BIOS setup etc. ...
I'm a beginner in assembly language and have noticed that the x86 code emitted by compilers usually keeps the frame pointer around even in release/optimized mode, when it could use the EBP register for something else. I undertand why the frame pointer might make code easier to debug, and might be necessary if alloca() is called within a...
Can increment of a register (in a loop) be used to determine the (effective) clock rate? I've naturally assumed it can, but I was commented that Cpu's may implant Super-scalar techniques that make this kind of computation useless. Also I was told that incrementing of registers on CPU can be done in less than one clock cycle. is it true...
I have became interested in C-like languages for performance computing. Can you recommend some alternative programming languages which have the following attributes: must be close to the hardware (bit fiddling, pointers or some alternative safe method like references) no managed code (no jvm/.net languages) has to be really fast (like ...