Buffering Block-oriented device
{"Image DocumentName": "Buffering Block-oriented device", "Image ImageDescription": "Perform input transfers in advance of requests being made and perform output transfers some time after the request is made. Block-oriented device. stores information in blocks that are usually of fixed size. transfers are made one block at a time. possible to reference data by its block number. disks and USB keys are examples. Stream-oriented device. transfers data in and out as a stream of bytes. no block structure. terminals, printers, communications ports, and most other devices that are not secondary storage are examples. The same considerations apply to an output operation. If a block is being. transferred from a user process area directly to an I/O module, then the process is. blocked during the transfer and the process may not be swapped out. To avoid these overheads and inefficiencies, it is sometimes convenient to. perform input transfers in advance of requests being made and to perform output. transfers some time after the request is made. This technique is known as buffering. In this section, we look at some of the buffering schemes that are supported by. operating systems to improve the performance of the system. In discussing the various approaches to buffering, it is sometimes important. to make a distinction between two types of I/O devices: block oriented and stream. oriented. A block-oriented device stores information in blocks that are usually of. fixed size, and transfers are made one block at a time. Generally, it is possible to. reference data by its block number. Disks and USB keys are examples of block oriented. devices. A stream-oriented device transfers data in and out as a stream of. bytes, with no block structure. Terminals, printers, communications ports, mouse. and other pointing devices, and most other devices that are not secondary storage. are stream oriented.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}