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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 this matrix example there exist two processes, two assets, a file, and a device. The first process is the owner of asset 1, has the ability to execute asset 2, read the file, and write some information to the device, while the second process is the owner of asset 2 and can read asset 1.
In addition to its literal meaning, the term may be applied to a situation when the data written by one circuit can be read only by other circuitry. The most common occurrence of the latter situation is when a processor writes data to a write-only register of hardware the processor is controlling. The hardware can read the instruction but the ...
One source of lock failure occurs when buffered I/O has buffers assigned in the user's local workspace, rather than in an operating system buffer pool. fread and fwrite are commonly used to do buffered I/O, and once a section of a file is read, another attempt to read that same section will, most likely, obtain the data from the local buffer ...
A Replay Protected Memory Block (RPMB) is provided as a means for a system to store data to the specific memory area in an authenticated and replay protected manner and can only be read and written via successfully authenticated read and write accesses. The data may be overwritten by the host but can never be erased.
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 ...
An RW lock allows concurrent access for read-only operations, whereas write operations require exclusive access. This means that multiple threads can read the data in parallel but an exclusive lock is needed for writing or modifying data. When a writer is writing the data, all other writers and readers will be blocked until the writer is ...
Reserved: The block is the only copy of the memory, but it is still coherent. No write-back is needed if the block is replaced. Dirty: The block is the only copy of the memory and it is incoherent. This copy was written one or more times. This is the only state that generates a write-back when the block is replaced in the cache.