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Abstract

I/O is either block-oriented (such as file I/O) or stream-oriented (such as network I/O). Streams are often slower than block devices (such as fixed disks) and read/write operations often cause the calling thread to block until input is available or output has been fully written. To compensate, modern operating systems let streams operate in, which makes it possible for a thread to read or write data without blocking. The operation fully succeeds or indicates partial success. Either way, the thread is able to perform other useful work instead of waiting.