Specifications

Introduction
1.7 Buffered and Direct I/O
data from the system buffer to the user buffer for a read request. Drivers
most often use buffered I/O for PIO devices such as line printers and card
readers.
The trade-off between buffered I/O and direct I/O is the time required to move the
data into the user’s buffer as against the time required to lock the buffer pages in
memory.
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