Analysis of information sources in references of the Wikipedia article "Memory address" in English language version.
The relocation procedure applies to the first 4,096 bytes of storage. This area contains all permanent storage assignments and, generally, has special significance to supervisory programs. The relocation is accomplished by inserting a 12-bit prefix in each address which has the high-order 12 bits set to zero and hence, pertains to location 0-4095.
Prefixing provides the ability to assign the block of real addresses containing assigned storage locations to a different block in absolute storage for each CPU, thus permitting more than one CPU sharing main storage to operate concurrently with a minimum of interference, especially in the processing of interruptions.
