What does Windows error code 120 (ERROR_CALL_NOT_IMPLEMENTED) mean?

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: The function is declared but is not implemented by the current Windows environment or provider.

Could be also:
Constant	Type	OS
EISNAM	errno	Linux
EPROTONOSUPPORT	errno	Solaris
ENODATA	errno	Windows
PHASE0_EXCEPTION	BugCheck Code	Windows

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ERROR_BAD_DRIVER_LEVEL	ERROR_SEM_TIMEOUT

ERROR_CALL_NOT_IMPLEMENTED

The requested function is not implemented

ERROR_CALL_NOT_IMPLEMENTED indicates that a callable entry point or operation exists at the interface level but the active platform, compatibility layer, or provider has no implementation for it.

What to check

Confirm the minimum supported Windows version for the function.
Check whether the call is being routed through a remote, legacy, or compatibility provider.
Use runtime feature detection instead of relying only on compile-time SDK availability.
Log the function and provider so the failure is distinguishable from a missing DLL export.

How to handle it

Choose a documented alternative when one exists. Repeating the same call without changing the environment will not make an unimplemented function succeed.

References

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