These are used in the values of ArchitecturesAllowed and ArchitecturesInstallIn64BitMode.
Matches systems capable of running 32-bit Arm binaries. Only Arm64 Windows includes such support.
Matches systems running Arm64 Windows.
Matches systems running 64-bit Windows, regardless of OS architecture.
This may be useful in an installer that doesn't ship any architecture-specific binaries, but requires access to something 64-bit, like HKLM64 in the [Registry] section, or the native 64-bit Program Files directory.
Matches systems capable of running x64 binaries. This includes systems running x64 Windows, and also Arm64-based Windows 11 systems, which have the ability to run x64 binaries via emulation.
Matches systems running x64 Windows only — not any other systems that have the ability to run x64 binaries via emulation.
In most cases, x64compatible should be used instead of x64os, because x64compatible allows x64 apps to be installed on Arm64 Windows 11 systems as well.
However, x64os is appropriate in unusual cases where an x64 app/binary is known to require true x64 Windows and cannot function under emulation. x64 device drivers are one example; x64 emulation isn't supported in kernel mode.
Before Inno Setup 6.3, x64os was named x64. The compiler still accepts x64 as an alias for x64os, but will emit a deprecation warning when used.
Matches systems capable of running 32-bit x86 binaries. This includes systems running x86 Windows, x64 Windows, and also Arm64 Windows 10 and 11 systems, which have the ability to run x86 binaries via emulation.
Given that Setup itself is currently always built as a 32-bit x86 binary, this always matches.
Matches systems running 32-bit x86 Windows only.
x86os usually only makes sense when installing 32-bit x86 device drivers. When installing a regular 32-bit app, x86compatible should be used instead (or just leave ArchitecturesAllowed unset).
Before Inno Setup 6.3, x86os was named x86. The compiler still accepts x86 as an alias for x86os.
See also:
Architecture Identifier Matchers like IsX64Compatible
ProcessorArchitecture