operating-system

问题 According to the book 'operating systems concepts', it says: With direct communication, each process that wants to communicate must explicitly name the recipient or sender of the communication. This scheme exhibits symmetry in addressing. In this scheme, the send and receive primitives are defined as: Send(P, message): Send a message to process P receive (Q, message)-Receive a message from process Q. In asymmetry only the sender names the recipient; the recipient is not required to name the

问题 I've been using python for a long time. python's system and subprocess methods can take shell=True attibute to spawn an intermediate process setting up env vars. before the command runs. I've be using Java back and forth and using Runtime.exec() to execute shell command. Runtime rt = Runtime.getRuntime(); Process process; String line; try { process = rt.exec(command); process.waitFor(); int exitStatus = process.exitValue(); } I find difficulty to run some commands in java with success like

问题 How to set a solid color as background in os x desktops programmatically? Have found the way to change it programmatically using the image. [[NSWorkspace sharedWorkspace]setDesktopImageURL:url forScreen:screen options:nil error:&error]; URL - image file url, screen - nsscreen object, error - nserror object. Would like to avoid the use of an external resource such as image files. Please help 回答1: fwiw I've often wanted to set my bg to white but that specific color is missing, the code below

问题 I haven't found a clear answer: does the control unit itself fetch pre-defined instructions to execute a cache eviction, or does the operating system intervene? If so, how? 回答1: Which part of the computer manages cache replacement? Typically; a cache manages cache replacement itself (its not done by a separate part). There are many types of caches where some are implemented by software (DNS cache, web page cache, file data cache) and some are implemented in hardware (instruction caches, data

问题 From the Tanenbaum OS book it is mentioned the following: "in user level threads, if a thread starts running, no other thread in that process will ever run unless the first thread voluntarily gives up the CPU". That means threads are going to run one after the other (sequently) not in parallel. So what is the advantage of the user-level threads? 回答1: There are two concepts of multitasking in a single process multiple thread environment. A single thread execute in time slice of the process.

问题 What are techniques for determining running OS in assembly language at runtime? If there are direct ways to determine this, that'd be awesome. I was also thinking of how there are tricks in Javascript to determine what browser you're running in... Are there similar techniques for determining OS or even CPU arch in a low level language like Intel assembly? Thanks, Chenz 回答1: CPU architecture will be next-to-impossible to determine. Machine code differs greatly between CPU architectures, and so

问题 I'm currently developing an OS kernel from scratch. I want to use a function to write characters on the screen , using the 0xB8000 memory location. the problem is the following : I use : void video_write(const unsigned char *string , char color ){ unsigned char *p = (unsigned char*) string ; char *c = (char*) (VIDEO_MEMORY ); //VIDEO_MEMORY is 0XB8000 while(*p != '\0') { *c = p[0] ; c++ ; *c = color ; c++ ; p++ ; } } void clear_screen(){ char *c = (char*) VIDEO_MEMORY ; int i = 0 ; for(i ; i

问题 From the man pages of OS161 : Synopsis #include <unistd.h> #include <fcntl.h> int open(const char *filename, int flags); int open(const char *filename, int flags, mode_t mode); How the standard c library function open is defined: int open(const char *filename, int flags, ...); The declaration: /* * Definition for each syscall. * All we do is load the syscall number into v0, the register the * kernel expects to find it in, and jump to the shared syscall code. * (Note that the addiu instruction

问题 Is it possible to detect, whether client system has specific windows application installed or not using Javascript? I developed one website, which would have to detect the application, which was developed by us only. But I want to let you know, the website name and windows application names are different. I mean consider my web application name is X and windows application name is Y not like same as Skype webapplication and Skype windows application Consider Skype, it has web application as

问题 I need to do some brute-force searching in process VA space for my study and hence would like limit my heap area's virtual address range. OS course told me that heap is anywhere between data and stack pages. So I want to shrink my process VA range by doing the following: Have a custom linker script that gave start and end of data somewhere very high in address range (0x7f45f88a6000) Tweak fs/binfmt_elf.c to have stack top as (0x8f45f88a6000) instead of randomly picking. Assume my program uses