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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. [5] Office 97, 2000, XP and 2003 use RC4 with 40 bits. [4]
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 .
It bypassed MS-DOS and directly accessed the disk, either via the BIOS or (preferably) 32-bit disk access (Windows-native protected mode disk drivers). This feature was a backport from the then-unreleased Windows 95, as suggested by Microsoft's advertisements for Windows for Workgroups 3.11 ("the 32-bit file system from our Chicago project").
In computing, protected mode, also called protected virtual address mode, [1] is an operational mode of x86-compatible central processing units (CPUs). It allows system software to use features such as segmentation, virtual memory, paging and safe multi-tasking designed to increase an operating system's control over application software.
using byte-range locks to arbitrate read and write access to regions within a single file [3] by Windows file systems disallowing executing files from being opened for write or delete access; Windows inherits the semantics of share-access controls from the MS-DOS system, where sharing was introduced in MS-DOS 3.3 . Thus, an application must ...
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 ...
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.
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.