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Write protect: When set, the CPU cannot write to read-only pages when privilege level is 0 18: AM: Alignment mask: Alignment check enabled if AM set, AC flag (in EFLAGS register) set, and privilege level is 3 29: NW: Not-write through: Globally enables/disable write-through caching: 30: CD: Cache disable: Globally enables/disable the memory ...
This often increases the speed of image write operations by several times, at the cost of losing the simple sequential read/write semantics of normal memory. Additional bits which are provided on some computer architectures , such as AMD64 , allow the shadowing of ROM contents in memory (shadow ROM), and the configuration of memory-mapped I/O .
These mechanisms are intended to prevent only accidental data loss or attacks by computer viruses. A determined user can easily circumvent them either by covering a notch with adhesive tape or by creating one with a punch as appropriate, or sometimes by physically altering the media transport to ignore the write-protect mechanism.
In Excel and Word 95 and prior editions a weak protection algorithm is used that converts a password to a 16-bit verifier and a 16-byte XOR obfuscation array [1] key. [4] Hacking software is now readily available to find a 16-byte key and decrypt the password-protected document.
Microsoft Write is a basic word processor [1] included with Windows 1.0 [2] and later, until Windows NT 3.51.Throughout its lifespan, it was minimally updated. "Microsoft Write" also shares the name of a commercial retail release of Microsoft Word for the Apple Macintosh and Atari ST which is otherwise separate from this program.
There may be a single page table, a page table for each process, a page table for each segment, or a hierarchy of page tables, depending on the architecture and the OS. The page tables are usually invisible to the process. Page tables make it easier to allocate additional memory, as each new page can be allocated from anywhere in physical memory.
Most file systems include attributes of files and directories that control the ability of users to read, change, navigate, and execute the contents of the file system. In some cases, menu options or functions may be made visible or hidden depending on a user's permission level; this kind of user interface is referred to as permission-driven.
Copy-on-write can be implemented efficiently using the page table by marking certain pages of memory as read-only and keeping a count of the number of references to the page. When data is written to these pages, the operating-system kernel intercepts the write attempt and allocates a new physical page, initialized with the copy-on-write data ...