Overview

Win32 Paths

Win32 paths are a living history of Microsoft OSes from DOS 1.0 through Windows 95/NT and modern Windows.

Type	Examples
Drive	`C:\Windows`
UNC	`\\server\share\`
Device	`\\.\PIPE\name`
Verbatim	`\\?\C:\Windows` `\\?\UNC\server\share\` `\\?\PIPE\name`

Paths are UTF-16 strings. Windows allows using other encodings (including UTF-8) but these are all lossily converted to and from UTF-16.

Filesystem drivers typically disallow the following characters in path components:

Disallowed	Description
`\` `/`	Path seperators
`:`	Dos drive and NTFS file stream separator
`*` `?`	Wildcards
`<` `>` `"`	DOS wildcards
`\|`	Pipe
`NUL` to `US`	ASCII control codes; aka Unicode C0 control codes (U+0000 to U+001F inclusive). Note that `DEL` (U+007F) is allowed.

Note that path separators and wildcards must be disallowed in normal filesystems otherwise some Win32 APIs will be unusable in some situations.

For legacy reasons, some filenames may be interpreted as DOS devices. This means, for example the path "AUX" will be rewritten as \\.\AUX.

The following are special dos device names:

AUX
CON
CONIN$
CONOUT$
COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9, COM², COM³, COM¹
LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8, LPT9, LPT², LPT³, LPT¹
NUL
PRN

Note that these names are case-insensitive though canonically they're uppercase.

Win32 paths are emulated on top of NT kernel paths. An NT path looks similar to a Unix path, except for the directory separator. For example:

\Device\HarddiskVolume2\directory\subdir\file.ext

These types of paths cannot be used directly in the Win32 API but can make themsevles apparent in other ways.