Showing results for History - The Old New Thing

Jun 10, 2009
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Why does MS-DOS use 8.3 filenames instead of, say, 11.2 or 16.16?

Raymond Chen
Raymond Chen

When I discussed years ago why operating system files tend to follow the old 8.3 file name convention, I neglected to mention why the old MS-DOS filename convention was 8.3 and not, say, 11.2 or 16.16. It's a holdover from CP/M. As I noted when I discussed the old MS-DOS wildcard matching rules, MS-DOS worked hard at being compatible with ...

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Jun 3, 2009
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What does the “Zw” prefix mean?

Raymond Chen
Raymond Chen

If you spend time in kernel mode, you're accustomed to seeing functions with two-letter (or occasionally, three-letter) prefixes that indicate which component they belong to. What does the "Zw" mean? Answer: Nothing. The people who chose the letters wanted to pick something that was unlikely to collide with anything. Perhaps they had a pr...

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Jun 1, 2009
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Why does the CreateProcess function modify its input command line?

Raymond Chen
Raymond Chen

One of the nasty gotchas of the function is that the parameter must be a mutable pointer. If you pass a pointer to memory that cannot be written to (for example, a pointer to a page that is marked ), then you might crash. Commenter Ritchie wonders why this parameter is so weird. Basically, somebody back in the 1980's wanted to avoid allocatin...

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Apr 23, 2009
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Why are there two values for PSH_WIZARD97?

Raymond Chen
Raymond Chen

Welcome, Slashdot readers. Remember, this Web site is for entertainment purposes only. If you go cruising through the commctrl.h header file, you'll find that there are two different definitions for PSH_WIZARD97: #if (_WIN32_IE >= 0x0400) ... #if (_WIN32_IE < 0x0500) #define PSH_WIZARD97 0x00002000 #else #define PSH_WIZARD97 ...

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Apr 17, 2009
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Why is the animation common control limited to RLE8-compressed animations?

Raymond Chen
Raymond Chen

The animation common control is very limited in the type of animations it can play. The animation must be in AVI format, it cannot have any sound, and it must be either uncompressed or use RLE8 compression. Why so many restrictions? Because if it could handle other file formats, play sound, and support arbitrary codecs, it would just be a reimple...

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Apr 7, 2009
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Clap and the filter graph claps with you

Raymond Chen
Raymond Chen

One of my colleagues was a fount of ideas, some of them crazy, some of them clever, and some of them both. I think this one counts as both. To render multimedia content with DirectShow, you build a so-called filter graph. A filter graph represents a series of transformations that are applied to data as it travels through the graph. For example, b...

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Apr 3, 2009
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On the almost-feature of floppy insertion detection in Windows 95

Raymond Chen
Raymond Chen

Gosh, that floppy insertion article generated a lot of comments. First, to clarify the table: The table is trying to say that if you had a Style A floppy drive, then issuing the magic series of commands would return 1 if a floppy was present, or 0 if the floppy was not present. On the other hand, if you had a Style B floppy drive, the...

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Apr 2, 2009
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Windows 95 almost had floppy insertion detection but the training cost was prohibitive

Raymond Chen
Raymond Chen

One feature which Windows 95 almost had was floppy disk insertion detection. In other words, Windows 95 almost had the ability to detect when a floppy disk was present in the drive without spinning up the drive. The person responsible for Windows 95's 32-bit floppy driver studied the floppy drive hardware specification and spotted ...

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Mar 3, 2009
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Why is there a dry fountain in the Redmond North campus?

Raymond Chen
Raymond Chen

One of the things that may strike you if you visit Microsoft's Redmond North campus is that there's a large, dry fountain outside the cafeteria. Why isn't the fountain running? The Redmond North campus was purchased from Safeco, and with the purchase, Microsoft obtained title to a fountain whose design had two fatal flaws: Having large qu...

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Feb 9, 2009
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What is the purpose of the RunAsCommand value?

Raymond Chen
Raymond Chen

Commenter c_e_pizano asks what the purpose of the registry value is. Well, for starters, it isn't documented, so the official answer to that question is "Don't mess with it." Kind of makes me wonder why you're asking about the registry value anyway, seeing as it's undocumented in the first place. Are you trying to reverse-engineer Windows? To...

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