NTSTATUS NTAPI
NtQuerySystemInformation (SYSTEMINFOCLASS sic,
                        PVOID           pData,
                        DWORD           dSize,
                        PDWORD          pdSize);
NTSTATUS NTAPI
NtSetSystemInformation (SYSTEMINFOCLASS sic,
                      PVOID           pData,
                      DWORD           dSize);

Example 1: The prototypes of NtQuerySystemInformation() and NtSetSystemInformation().