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 | I think this is because you also copy null or ambigious bytes trailing the actual input string into the reversed one. For instance "abc" may be last 3 bytes of 80 byte reverse buffer as the first 77 is ambigous (most likely null's). Using push/pop is more complicated then it …  |
| | In my opinion its bad practice to do that. Though as already said its valid if EBX remains unchanged after the function returns.  |
| | INT 21h are DOS interrupts not ment to be used in Windows. |
| | Re: NASM Boot Disk Hi, It doesn't work because you've not set up DS segement register, as of what you have in the code, its ambigous and while your at it, its best to leave other regularly used segment registers defined rather keeping them ambigous. In x86 assembly, when you don't specify which segment … |
| | Hmm the original state before a jump is to not do a jmp at all or patching the jmp opcodes with nop's. Obviously this isnt MASM but a dissassembled binary. If you mean restoring the state before a push, you need to add into ESP register, poping this into a … |
 | Yup. Look at these lines: [code] a byte 1,3,5,7,9 ......... mov esi,offset a mov ecx,5 L11: mov eax,[esi] [/code] Obviously there is size conflicts. eax register is 32bits remeber and your data type is 8bits. The remedy is you either declare 32bit datatypes for "a" array & "b" array and … |
 | [quote=Narue;285285]>without calls to the operating system, the code is as portable as could be wished for OS wise. The assembly code might be portable, the machine code cannot be. For example, you can assemble a COFF program on Windows and it won't work on Linux because the two systems use … |
 | Back in DOS days the FPU was software emulated by an interrupt which a modern processor should never interrupt to. In otherwords you'll need the CPU to trigger that interrupt, a ancient system that does not have a FPU which is pretty rare to have.. It [I]did[/I] or may even … |
| | For information on BIOS/DOS interrupt services you can retrieve them in a well known site - ralphs brown interrupt list: [URL]http://www.ctyme.com/intr/int.htm[/URL] I wont be doing your dirty work. If you would of put some time and research a bit you'll find its not hard to comment this yourself. |
| | If you ask me, this isn't so efficent when it comes to instruction prefetch caches. These days its better to loop then unroll them. :) |
| | Re: counting digits [quote=kiks;289455]Does anyone knows how can I count how many digits are there in a binary number? Any ideas???[/quote] From what I understand, you want to count the number of digits in binary form, ex. 10001 (decimal 17) has 5 digits. You simply test the most significant towards least significant bits … |
| | 32 byte dividend is enormous.. out of curiousity why do you have to divide such a precised or huge number? Secondly, what is exactly efficent, the code algorithm in size or how fast can you produce the results? Also, how big should we expect the divisor to be? And lastly … |
| | 9A 06 00 70 00 == call far absolute 0070:0006h (706h) Typically the assemblers will generate relative calls insted of absolute, unless in the source you directly give it an abosute address, which is my guess to what is going on. If this is the case you should be using … |
| | [quote=belhifet;259550] Is assembly worth learning it? I know that everything you learn can only be an advantage, but sometimes I just get the feeling that I'm wasting my time with Assembly. I've got a huge list of books that I want to read and I just want to be sure … |
| | [quote=asm_2;263032]-So why are there no smarter .exe files that orders the instructions for your I/O-usage?[/quote] If you mean why the compiler doesn't reorder those instructions to optimise, its simply because compilers don't know what the hardware is. Most I/Os require some things sequenced which cannot be reordered. |
| | Re: Reuest To All It would of been a lot quicker to get to the point and ask the actual question, now you gotta reply with the question and wait for another reply. Anyway, I've been using MASM quite some time now and I'm sure theres few others who will have some knowledge on … |
| | Are you sure you want to mess with the BIOS firmware first of all? Be aware that its typical for any kernel to rely on some BIOS interrupt services, and more importantly the firmware have code to configure your system during boot, such as PCI, ISA, PNP confiurations, and other … |
| | [quote=uu666;245349] Selector is used as an index to select the descriptor from descriptors table. Where is located (if i can say thus) that logical address and the descriptors table (somehow in physical memory?) Thanks.[/quote] I'm not 100% sure what your trying to ask, but I'm guessing its on the lines … |
 | 1. Your OS has a video card driver? 2. Your OS has implemented a HAL? (Hardware Abstraction Layer?) If #1 is not met, but have #2 in your OS you can start by supplying a VESA compliant driver. If both are not met, better start working on a driver interface …  |
| | Re: Clock cycles You will basically have to come up with a code to test the frequency of the processor, which is basically a while loop that counts the clocks within a time frame. To find the frequency of older processors such as the 80386 which does not have the RDTSC instruction, will …  |