A floating-point format is a data structure specifying the fields that comprise a floating-point numeral, the layout of those fields, and their arithmetic interpretation. A floating-point storage format specifies how a floating-point format is stored in memory. The IEEE standard defines the formats, but the choice of storage formats is left to the implementers.
Assembly language software sometimes relies on using the storage formats, but higher level languages usually deal only with the linguistic notions of floating-point data types. These types have different names in different high-level languages, and correspond to the IEEE formats as shown in Table 2–1.
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IEEE 754 specifies exactly the single and double floating-point formats, and it defines a class of extended formats for each of these two basic formats. The long double and REAL*16 types shown in Table 2–1 refer to one of the class of double extended formats defined by the IEEE standard.
The following sections describe in detail each of the storage formats used for the IEEE floating-point formats on SPARC and x86 platforms.