For example, if the address in a protocol header is 16 bits long, the address space is 64 kilobytes( KB), with 32 bits up to 4 gigabytes( GB) and with 64 bits up to 512 terabytes( TB) can be addressed.
InPC technology, this is the maximum number of components or memory locations in the main memory that can be addressed by the central processing unit( CPU). In hard disk addressing, the address space results from the number of cylinders, read/write heads and sectors per track. There are 16 bits available for the addressable cylinders, 4 bits for the number of addressable heads and 8 bits (-1) for the sectors per track. This results in a theoretical hard disk address space of 127.5 gigabytes (GB).