How large is a DWORD with 32- and 64-bit code?

Question

In Visual C++ a DWORD is just an unsigned long that is machine, platform, and SDK dependent. However, since DWORD is a double word (that is 2 * 16), is a DWORD still 32-bit on 64-bit architectures?

This is a nitpick but technically this question applies to either C or C++, it might be better to remove the C++ tag or add the C tag, but I'm not sure which one is better. — jrh, Dec 26 '17 at 21:05

score 70 · Accepted Answer · edited Jan 27 '10 at 00:40

70

Actually, on 32-bit computers a word is 32-bit, but the DWORD type is a leftover from the good old days of 16-bit.

In order to make it easier to port programs to the newer system, Microsoft has decided all the old types will not change size.

You can find the official list here: http://msdn.microsoft.com/en-us/library/aa383751(VS.85).aspx

All the platform-dependent types that changed with the transition from 32-bit to 64-bit end with _PTR (DWORD_PTR will be 32-bit on 32-bit Windows and 64-bit on 64-bit Windows).

edited Jan 27 '10 at 00:40

Daniel Naab

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answered Sep 02 '08 at 13:02

Nir

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The actual ranges are listed [here](https://msdn.microsoft.com/en-us/library/s3f49ktz.aspx). – Laurie Stearn Apr 02 '16 at 12:19
@LaurieStearn I think this article is about the data types that the Microsoft compilers use internally, not the winapi data types like `DWORD`. – jrh Dec 26 '17 at 21:02
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Yeah, the article in the answer's linked [official list](https://msdn.microsoft.com/en-us/library/aa383751(VS.85).aspx) now has the ranges: Quote: **DWORD: A 32-bit unsigned integer. The range is 0 through 4294967295 decimal.** – Laurie Stearn Dec 27 '17 at 03:02
DWORD is on the windows libraries equal to an "unsigned long" – jaques-sam Dec 05 '18 at 12:23

score 17 · Answer 2 · answered Sep 02 '08 at 12:55

It is defined as:

typedef unsigned long       DWORD;

However, according to the MSDN:

On 32-bit platforms, long is synonymous with int.

Therefore, DWORD is 32bit on a 32bit operating system. There is a separate define for a 64bit DWORD:

typdef unsigned _int64 DWORD64;

Hope that helps.

score 12 · Answer 3 · answered Sep 02 '08 at 12:55

12

No ... on all Windows platforms DWORD is 32 bits. LONGLONG or LONG64 is used for 64 bit types.

answered Sep 02 '08 at 12:55

Rob Walker

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it has nothing to do with Windows, it's Intel term – Abyx Jul 16 '13 at 17:48
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@Abyx: the typedef `DWORD` is very Windows. – rubenvb Jul 16 '13 at 19:53
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@rubenvb, oh and why it's called `DWORD` and not something else like `QBYTE` or `DUBWD`? – Abyx Jul 16 '13 at 20:47

score 1 · Answer 4 · answered Aug 15 '22 at 20:21

1

Windows API defines DWORD sizes as follows:

x86: sizeof(DWORD) = 4
x64: sizeof(DWORD) = 4

answered Aug 15 '22 at 20:21

ogggre

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How large is a DWORD with 32- and 64-bit code?

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