INF BitReg Directive

Note  If you are building a universal or mobile driver package, this directive is not valid. See Using a Universal INF File.

A BitReg directive references one or more INF-writer-defined sections used to set or clear bits within an existing REG_BINARY-type value entry in the registry. However, this directive is very rarely used in device/driver INF files.

[DDInstall] | 
[DDInstall.HW] | 
[DDInstall.CoInstallers] | 
[ClassInstall32] | 
[ClassInstall32.ntx86] | 
[ClassInstall32.ntia64] |  (Windows XP and later versions of Windows)
[ClassInstall32.ntamd64]  (Windows XP and later versions of Windows)
[ClassInstall32.ntarm]  (Windows 8 and later versions of Windows)
[ClassInstall32.ntarm64]  (Windows 10 and later versions of Windows)


A BitReg directive can be specified under any of the sections shown in the formal syntax statement above. This directive can also be specified under any of the following INF-writer-defined sections:

  • A service-install-section or event-log-install section referenced by the AddService directive in a DDInstall.Services section.
  • An add-interface-section referenced by the AddInterface directive in a DDInstall.Interfaces section.
  • An install-interface-section referenced in an InterfaceInstall32 section

Each named section referenced by a BitReg directive has the following form:

reg-root, [subkey], value-entry-name, [flags], byte-mask, byte-to-modify
reg-root, [subkey], value-entry-name, [flags], byte-mask, byte-to-modify

A bit-registry-section can have any number of entries, each on a separate line.


Identifies the root of the registry tree for other values supplied in this entry. The value can be one of the following:

Abbreviation for HKEY_CLASSES_ROOT.

Abbreviation for HKEY_CURRENT_USER.

Abbreviation for HKEY_LOCAL_MACHINE.

Abbreviation for HKEY_USERS.

Relative root − that is, keys that are specified by using this abbreviation are relative to the registry key associated with the INF section in which this BitReg directive appears, as indicated in the following table.

INF Section Containing BitReg Directive Registry Key Referenced by HKR
INF DDInstall section The device's software key
INF DDInstall.HW section The device's hardware key
INF DDInstall.Services section The Services key

Note  HKR cannot be used in a bit-registry-section referenced from an INF DefaultInstall section.

For more information about driver information that is stored under the HKEY_LOCAL_MACHINE root, see Registry Trees and Keys for Devices and Drivers.

This optional value, expressed either as a %strkey% token defined in a Strings section of the INF or as a registry path under the given reg-root (key1\key2\key3...), specifies the key that contains the value entry to be modified.

Specifies the name of an existing REG_BINARY-type value entry in the (existing) subkey to be modified. It can be expressed either as "quoted string" or as a %strkey% token that is defined in the INF's Strings section.

This optional hexadecimal value, expressed as an ORed bitmask of system-defined low word and high word flag values, specifies whether to clear or set the bits specified in the given byte-mask. Its default value is zero, which clears the bits in the 64-bit section of the registry.

Bitmask values for each of these flags are as follows:

Clear the bits specified by byte-mask.

Set the bits specified by byte-mask.

0x00004000 (FLG_BITREG_32BITKEY)
(Windows XP and later versions of Windows.) Make the specified change in the 32-bit registry. If not specified, the change is made to the native registry.

This byte-sized mask, expressed in hexadecimal notation, specifies which bits to clear or set in the current value of the given value-entry-name.

This byte-sized value, expressed in decimal, specifies the zero-based index of the byte within the REG_BINARY-type value to be modified.


Each bit-registry-section name must be unique to the INF file, but it can be referenced by BitReg directives in other sections of the same INF. Each INF-writer-created section name must be unique within the INF file and must follow the general rules for defining section names. For more information about these rules, see General Syntax Rules for INF Files.

The value of an existing REG_BINARY-type value entry can also be modified by overwriting its current value within an add-registry section elsewhere in the INF file. For more information about add-registry sections, see the reference for the AddRegdirective.

Using a BitReg directive requires the definition of another INF file section. However, the value of an existing REG_BINARY-type value entry can be modified bit-by-bit in such a section, thereby preserving the values of all remaining bits.


The following example shows a bit-registry section for a fictional application.

; set first bit of byte 0 in ProgramData value entry
; preceding would change value 30,00,10 to 31,00,10

; clear high bit of byte 2 in ProgramData value entry
; preceding would change value 30,00,f0 to 30,00,70

; set second and third bits of byte 1 in ProgramData value entry
; preceding would change value 30,00,f0 to 30,06,f0

See also