base0F

Base0F is not a single standardized term, but a label that may appear in technical discussions to refer to two related notions in computing. In the most common usage, base0F points to the 0F prefix in the x86 instruction set. The byte 0x0F acts as an escape prefix that modifies the meaning of the following opcode byte, enabling a set of extended two-byte opcodes. This mechanism expands the opcode space beyond the primary, one-byte opcodes and is central to many instructions in both legacy and modern x86 machines. The 0F prefix is used in combination with other prefixes and opcode bytes to specify instructions, including those used in xmm and other extended instruction families. The exact operation encoded depends on the following byte, so 0F cannot be interpreted independently.

In other contexts, base0F can sometimes be used to discuss numeral bases in a nonstandard or informal way. In such cases it might denote a base-15 (digits 0–9 and A–E) system, or be used as a stylistic shorthand in documentation to invoke hexadecimal familiarity while referring to a non-hex base. However, base-15 notation is not widely standardized or supported in mainstream programming libraries, and it is largely of theoretical or niche interest rather than practical use.

Because base0F is not a single, formal standard, readers should rely on surrounding context to determine whether it refers to the x86 0F opcode prefix or to an informal discussion of nonstandard numeral bases. See also: 0x0F prefix, extended opcode map, x86 instruction encoding, and base numeral systems.