What Does the Zw Prefix Mean?

The Windows native system services routines have names that begin with the prefixes Nt and Zw. The Nt prefix is an abbreviation of Windows NT, but the Zw prefix has no meaning. Zw was selected partly to avoid potential naming conflicts with other APIs, and partly to avoid using any potentially useful two-letter prefixes that might be needed in the future.

Many of the Windows driver support routines have names that begin with two- or three-letter prefixes. These prefixes indicate which kernel-mode system components implement the routines. The following table contains some examples.

PrefixKernel componentExample routine

Cm

Configuration manager

CmRegisterCallbackEx

Ex

Executive

ExAllocatePool

Hal

Hardware abstraction layer

HalGetAdapter

Io

I/O manager

IoAllocateIrp

Ke

Kernel core

KeSetEvent

Mm

Memory manager

MmUnlockPages

Ob

Object manager

ObReferenceObject

Po

Power manager

PoSetPowerState

Tm

Transaction manager

TmCommitTransaction

Nt and Zw

Native system services

NtCreateFile and ZwCreateFile

 

 

 

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