tailieunhanh - The Little Black Book of Computer Viruses phần 3

Untraceable triển khai là một chìa khóa để tránh bị đưa ra xét xử vì tội phản quốc, gián điệp, phá hoại. Trong số các phức tạp nhất của các lập trình máy tính, virus máy tính là phương tiện của sự lựa chọn cho việc triển khai mã phá hoại. | 30 The Little Black Book of Computer Viruses for the operating system about how to handle the file. The FAT is a map of the entire disk which simply informs the operating system which areas are occupied by which files. Each disk has two FAT s which are identical copies of each other. The second is a backup in case the first gets corrupted. On the other hand a disk may have many directories. One directory known as the root directory is present on every disk but the root may have multiple subdirectories nested one inside of another to form a tree structure. These subdirectories can be created used and removed by the user at will. Thus the tree structure can be as simple or as complex as the user has made it. Both the FAT and the root directory are located in a fixed area of the disk reserved especially for them. Subdirectories are stored just like other files with the file attribute set to indicate that this file is a directory. The operating system then handles this subdirectory file in a completely different manner than other files to make it look like a directory and not just another file. The subdirectory file simply consists of a sequence of 32 byte records describing the files in that directory. It may contain a 32 byte record with the attribute set to directory which means that this file is a subdirectory of a subdirectory. The DOS operating system normally controls all access to files and subdirectories. If one wants to read or write to a file he does not write a program that locates the correct directory on the disk reads the file descriptor records to find the right one figure out where the file is and read it. Instead of doing all of this work he simply gives DOS the directory and name of the file and asks it to open the file. DOS does all the grunt work. This saves a lot of time in writing and debugging programs. One simply does not have to deal with the intricate details of managing files and interfacing with the hardware. DOS is told what to do using .