The Free On-line Dictionary of Computing (30 December 2018):
1. Computer memory, usually magnetic disks,
storing data and programs. Sections of this information can
then be copied into the main memory (RAM) for processing.
Backing store is cheaper but RAM is faster. Such a hierarchy
of memory devices allows a trade-off between performance and
2. Character storage in memory or on disk, as opposed
to displayed or printed characters. This distinction is
important where the visual ordering of characters differs from
the order in which they are stored, e.g. bidirectional or
In a Unicode encoding, text is stored in sequential order in
the backing store. Logical or backing store order corresponds
to the order in which text is typed on the keyboard (after
corrections such as insertions, deletions, and overtyping). A
text rendering process converts Unicode text in the backing
store to readable text.
["The Unicode Standard: Worldwide Character Encoding", Version
1.0, Vol. 1. Addison-Wesley, 1991].