Figure 2-33. Auxiliary storage supplements the main storage.
d. Storage Addressing. The main storage of a computer can be thought to
resemble the numbered mailboxes in a post office. Each mailbox is located and
identified by its number. In a similar way, main storage is divided into locations, each
with a unique address. Each location holds a specific unit of data for use by the central
processor. A unit of data tan be a digit, a character, a byte, a word, or a record. Each
item of data is inserted into or extracted from a specific storage location. Whenever
data are inserted into a storage location, they replace the previous contents of that
location. When data are extracted from a location, the contents remain unchanged
since only a copy of the contents has actually been removed. Once data are placed in
storage, therefore, they may be used many times.
Figure 2-34. Main storage may be thought to resemble a series of numbered