In computing, an address space defines a range of discrete addresses, each of which may correspond to a network host, peripheral device, disk sector, a memory cell or other logical or physical entity.
For software programs to save and retrieve stored data, each datum must have an address where it can be located.
In the case of total order, as for memory addresses, these are simply chunks.
Then, for a disk drive connected via Parallel ATA, each of them must be converted to logical cylinder-head-sector address due to the interface historical shortcomings.
It is converted back to LBA by the disk controller, then, finally, to physical cylinder, head and sector numbers.