greater value than older products. Digital preservation relies on the continuous maintenance and usage of hardware and software formats, which the threat of obsolescence can interfere with. Four types of digital obsolescence exist in the realm of hardware and software access:. Functional obsolescence, or the mechanical failure of a device that prevents information access, which can be the result of damage through rough handling, gradual wear from extended usage, or intentional failure through planned obsolescence; Postponement obsolescence, or intentionally upgrading some information systems within an institution, but not all of them, that is often implemented as part of a "security through obsolescence" strategy; Systemic obsolescence, or deliberate design changes made to programs and applications so that newer updates are increasingly incompatible with older versions, forcing the user to purchase newer software editions or hardware; Technical obsolescence, or the adoption of newer, more accessible technologies with the intention to replace older, often outdated software or hardware, occurring on the side of the consumer or manufacturer. Examples of digital obsolescence Because the majority of digital information relies on two factors for curation and retrieval, it is important to separately classify how digital obsolescence impacts digital preservation through both hardware and software mediums. Hardware Hardware concerns are two-fold in archival and library fields: in addition to the physical storage medium of magnetic tape, optical disc, or solid-state computer memory, a separate electronic device is often required for information access. And while proper storage can help mitigate some environmental vulnerabilities to storage formats (including dust, humidity, radiation, and temperature) and extend preservation for decades, there are other inevitable endangering factors. Magnetic tape and floppy disks are vulnerable to both the deterioration of adhesive holding the magnetic data layer to its backing or the demagnetization of the data layer, commonly called "bit rot"; optical discs are specifically susceptible to physical damage to their readable surface, and to oxidation occurring between improperly sealed outer layers; a process referred to as "disc rot" or, inaccurately, "laser rot" (particularly in reference to LaserDiscs). Older forms of floating-gate MOSFET based read-only-memory storage such as (some) cartridges and (most) memory cards encounter their own form of bit rot when the charges representing individual bits of binary information dissipate beyond a certain level (called "flipping") and the data is rendered unreadable. The operability of a format’s appropriate playback or recording device possess their own vulnerabilities. Cassette decks and disk drives rely