DGCs are backed by gold through unallocated or allocated gold storage. Banks may issue gold certificates for gold that is "allocated" (fully reserved) or "unallocated" (pooled). The material was recovered after the overwrite attempts from unallocated space. IPv4 address exhaustion is the depletion of the pool of unallocated IPv4 addresses. Two channels were to put on reserve and the remaining two were unallocated (future use). Prefixes for those stations are either unallocated or unavailable by ITU definitions. The areas of unallocated address space are called the bogon space. The directory consists of an array of entries, one per file or unallocated space. This resulted in a large amount of unallocated numbers. Blocks marked as such remain unallocated from then on. The regions are iteratively grown by comparison of all unallocated neighboring pixels to the regions. This left five reserved but unallocated /8 blocks. It tracks when memory is freed or "unallocated" and updates the status. In addition, each current area code has large number "ranges" unallocated. This created four unallocated delegates, whose status was to be determined later.