NtQueryInstallUILanguage - NtDoc

#ifndef _NTEXAPI_H
#if (PHNT_MODE != PHNT_MODE_KERNEL)

NTSYSCALLAPI
NTSTATUS
NTAPI
NtQueryInstallUILanguage(
    _Out_ LANGID *InstallUILanguageId
    );

#endif
#endif
View code on GitHub

#ifndef _NTZWAPI_H

NTSYSCALLAPI
NTSTATUS
NTAPI
ZwQueryInstallUILanguage(
    _Out_ LANGID *InstallUILanguageId
    );

#endif
View code on GitHub