Fat binary
combined executable file for multiple processor types or operating systems
A fat binary (or multiarchitecture binary) is a computer executable program or library which has been expanded (or "fattened") with code native to multiple instruction sets which can consequently be run on multiple processor types. This results in a file larger than a normal one-architecture binary file, thus the name.
The usual method of implementation is to include a version of the machine code for each instruction set, preceded by a single entry point with code compatible with all operating systems, which executes a jump to the appropriate section. Alternative implementations store different executables in different forks, each with its own entry point that is directly used by the operating system.
The use of fat binaries is not common in operating system software, except on NeXTSTEP and NeXTSTEP-derived Apple operating systems such as macOS and iOS (see below); there are several alternatives to solve the same problem, such as the use of an installer program to choose an architecture-specific binary at install time (such as with Android multiple APKs), selecting an architecture-specific binary at runtime (such as with Plan 9's union directories and GNUstep's fat bundles), distributing software in source code form and compiling it in-place, or the use of a virtual machine (such as with Java) and just-in-time compilation.
Apollo
Apollo's compound executables
In 1988, Apollo Computer's Domain/OS SR10.1 introduced a new file type, "cmpexe" (compound executable), that bundled binaries for Motorola 680x0 and Apollo PRISM executables.
Apple
Apple's fat binary
A fat-binary scheme smoothed the Apple Macintosh's transition, beginning in 1994, from 68k microprocessors to PowerPC microprocessors. Many applications for the old platform ran transparently on the new platform under an evolving emulation scheme, but emulated code generally runs slower than native code. Applications released as "fat binaries" took up more storage space, but they ran at full speed on either platform. This was achieved by packaging both a 68k-compiled version and a PowerPC-compiled version of the same program into their executable files.
Begin with the source’s own compact description: “Fat binary” is combined executable file for multiple processor types or operating systems. The dossier treats that line as a proposition to test through binary, combined and executable, not as a finished interpretation.
Why this record matters
The phrase “combined executable file for multiple processor types or operating systems” supplies a clear boundary for inquiry. It also exposes the unanswered questions: who defined that boundary, when it became stable and which sources sit outside it.
The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Jun 29, 2026. The linked authority identifier is Q1397886. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1988 and 1994.
A concise general-reference account can conceal disagreements about scope, terminology or the weight assigned to individual sources. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
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This entry incorporates text from “Fat binary” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.