An Introduction To DWORD Values

Other articles on this website have explained the basic structure of the Windows Registry, from the five main Root Keys (Hives) of HKCR / HKCU / HKLM / HKU / HKCC, through to their various Keys and SubKeys.

In this article we will look at a common Registry key/subkey "value" called the DWORD.

VALUES

When we define a Registry key all we have done is describe a "path" that leads us to the actual information that the Windows computer needs. The Registry stores all its information in what are called Value Entries. Each Value is made up of three parts: Name, Data and Type - see Fig 1.0 below.

In the Windows Registry Editor (Regedit.exe) there are panes. The left pane contains the key's/subkey's and the right hand pane contains the values and is known as the value pane

Fig 1.0 - The Registry Editor Value Pane

A key and subkey can have more than one value associated with them, and in fact it is normal to find many values present. Every key needs a value and the first is always called the DEFAULT. The Value Name has to be unique to each key or subkey; however it can be used again in another key or subkey without problems.

The Value Data depends on the Value Type but it is worth noting that it can be empty, null or contain data. Value Data can be a string of text, hexadecimal notation or decimal notation.

TYPES

Every Value has what is called a Value Type. This is used to describe the kind of data that it contains.

As an example, if you open up My Documents on your computer you will probably see text documents, Word documents, PDF documents, Excel documents and many others.

These ALL have a document extension so that your computer can recognise them and know how to treat them e.g. .txt, .doc, .pdf and .xls.

This is very similar with Value Entries in the Registry. There are different “types” of data used in the Registry that the computer can understand and take action on. There are around 15 different Value Types of which only 5 are only actually seen very often.

The DWORD Value

REG_DWORD, or just plain DWORD as it is often known as, is the most common Value Type found in the Registry. The DWORD value entry can consist of 32 bit numbers expressed in decimal or hexadecimal notation, for example: 622675 or 0x00098053

The DWORD value entry can also consist of an entry into the Registry that is measured in time. It will always be expressed as Milliseconds and be in Decimal so a DWORD value of the entry of 4 hours is shown as 14400000 - see Fig 1.1.

Fig 1.1 - A REG_DWORD Showing 4 Hours As Milliseconds

The DWORD value entry is commonly used when you want to create a Value Type that is a True or False entry (called a Boolean flag). For example: where 0 = Enable (True) and 1 = Disable (False). See Fig 1.2.

Fig 1.2 - A REG_DWORD Showing a True or False entry

The term DWORD simply stands for "double word." A word is the natural unit of computing, when Windows was originally developed, the system word size on Intel x86 processors was 16 bits. Consequently, WORD was defined as being 16 bits and DWORD as 32.

Today however we now have 64 bit processors and so 64bit word sizes, but the term DWORD remains in use.

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