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The “devtab” structure has five words, the last four of which are forward and backward pointers.
One instance of “devtab” is declared within the device handler for each block type of peripheral device. For our model system the only block device is the RK05 disk, and “rktab” is declared as a “devtab” structure at line 5386.
The “devtab” structure contains some status information for the the device and serves as a list head for:
the list of buffers associated with the device, and simultaneously on the “av”-list;
the list of outstanding i/o requests for the device.
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