CS计算机代考程序代写 Disc operations

Disc operations

devctl(DC_DISC_CHECK, Unit)

returns the number of blocks on disc drive Unit (1 to 8)
returns 0 if the indicated disc is not available
or -2 if the parameter could not be read
or -3 if the unit number UN is not in range 1 to 8

devctl(DC_DISC_READ, Unit, FirstBlock, NumberOfBlocks, MemAddress)

reads the indicated blocks into memory starting at MemAddress.
MemAddress must point to at least NumberOfBlocks*128 words of memory.
returns number of blocks actually read
or -2 if the parameters could not be read
or -3 if the unit number UN is not available
or -4 if a block number is out of range
or -5 if MemAddress could not be read from

devctl(DC_DISC_WRITE, Unit, FirstBlock, NumberOfBlocks, MemAddress)

writess the indicated blocks from memory starting at MemAddress.
MemAddress must point to at least NumberOfBlocks*128 words of memory.
returns number of blocks actually written
or -2 if the parameters could not be read
or -3 if the unit number UN is not available
or -4 if a block number is out of range
or -5 if MemAddress could not be written to
or -6 if it could not write all of the data to disc