24-11-2012, 05:48 PM
2 Marks Questions
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Spooling
1) Spooling is the process of a sending data to a spool, or temporary storage area in the computer's memory. This data may contain files or processes. Like a spool of thread, the data can build up within the spool as multiple files or jobs are sent to it. However, unlike a spool of thread, the first jobs sent to the spool are the first ones to be processed (FIFO, not LIFO).
The most common type of spooling is print spooling, where print jobs are sent to a print spool before being transmitted to the printer. For example, when you print a document from within an application, the document data is spooled to a temporary storage area while the printer warms up. As soon as the printer is ready to print the document, the data is sent from the spool to the printer and the document is printed.
Print spooling gets its name from technology used in the 1960s, when print jobs were stored on large reels of magnetic tape. The data from these reels was physically spooled to electrostatic printers, which printed the output saved to the tape.
Thrashing (computer science)
In computer science, thrashing is a situation where large amounts of computer resources are used to do a minimal amount of work, with the system in a continual state of resource contention.[1][2][3] Once started, thrashing is typically self-sustaining until something occurs to remove the original situation that led to the initial thrashing behavior.
Usually thrashing refers to two or more processes accessing a shared resource repeatedly such that serious system performance degradation occurs because the system is spending a disproportionate amount of time just accessing the shared resource. Resource access time may generally be considered as wasted, since it does not contribute to the advancement of any process. This is often the case when aCPU can process more information than can be held in available RAM; consequently the system spends more time preparing to execute instructions than actually executing them.
Fragmentation
(1) Refers to the condition of a disk in which files are divided into pieces scattered around the disk. Fragmentation occurs naturally when you use a disk frequently, creating, deleting, and modifying files. At some point, the operating system needs to store parts of a file in noncontiguous clusters. This is entirely invisible to users, but it can slow down the speed at which data is accessed because the disk drive must search through different parts of the disk to put together a single file.
In DOS 6.0 and later systems, you can defragment a disk with the DEFRAGcommand. You can also buy software utilities, called disk optimizers ordefragmenters, that defragment a disk.
Memory segmentation
Memory segmentation is the division of computer memory into segments or sections. Segments or sections are also used in object filesof compiled programs when they are linked together into a program image, or the image is loaded into memory. In a computer system using segmentation, a reference to a memory location includes a value that identifies a segment and an offset within that segment.
Different segments may be created for different program modules, or for different classes of memory usage such as code and data segments. Certain segments may even be shared between programs.[1]
What is disk formatting?
• Disk formatting is the process of preparing a hard disk or other storage medium for use, including setting up an empty file system. A variety of utilities and programs exist for this task.
Large disks can be partitioned, that is, divided into distinct sections that are each formatted with their own file systems. This is normally only done on hard disks because of the small sizes of other disk types, as well as compatibility issues.
Memory management
Memory management is the act of managing computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and freeing it for reuse when no longer needed. This is critical to the computer system.
Several methods have been devised, that increase the effectiveness of memory management. Virtual memory systems separate the memory addresses used by a process from actual physical addresses, allowing separation of processes and increasing the effectively available amount of RAM using paging or swapping to secondary storage. The quality of the virtual memory manager can have a big impact on overall system performance.