DevHlp services include

Service                 Code    Description
DevHlp_CloseFile        80h     Close file (system
                                initialization time only)
DevHlp_FreeCtxHook      64h     Free context hook
DevHlp_FileOpen         7Fh     Open file (at initialization)
DevHlp_GetDosVar        24h     Return address of kernel
                                variable
DevHlp_KillProc         7Dh     Kill process unconditionally
DevHlp_OpenFile         7Fh     Open file (system initialization
                                time only)
DevHlp_PerfSysTrace     45h     Write Software Trace information
                                to STRACE buffer
DevHlp_QSysState        7Eh     Get system status information
DevHlp_ReadFile         81h     Read (system initialization time
                                only)
DevHlp_ReadFileAt       82h     Seek and read (system
                                initialization time only)
DevHlp_RegisterKDD      83h     Register driver with kernel
                                debugger
DevHlp_SysTrace         28h     Add information to System Trace
                                buffer

System event notification

Event                 Index     Description
event_POWER           9         Power off event