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Jan 11, 2005
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Why doesn't \ autocomplete to all the computers on the network?

Raymond Chen

Wes Haggard wishes that \ would autocomplete to all the computers on the network. [Link fixed 10am.] An early beta of Windows 95 actually did something similar to this, showing all the computers on the network when you opened the Network Neighborhood folder. And the feature was quickly killed. Why? Corporations with large networks wer...

History
Jan 11, 2005
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Why doesn’t \ autocomplete to all the computers on the network?

Raymond Chen

Wes Haggard wishes that \ would autocomplete to all the computers on the network. [Link fixed 10am.] An early beta of Windows 95 actually did something similar to this, showing all the computers on the network when you opened the Network Neighborhood folder. And the feature was quickly killed. Why? Corporations with large networks wer...

History
Dec 20, 2004
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Don’t save anything you can recalculate

Raymond Chen

Nowadays, a major barrier to performance for many classes of programs is paging. We saw earlier this year that paging can kill a server. Today, another example of how performance became tied to paging. The principle is "Don't save anything you can recalculate." This of course, seems counterintuitive: Shouldn't you save the answer so you don't h...

History
Dec 17, 2004
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How did Windows 95 rebase DLLs?

Raymond Chen

Windows 95 handled DLL-rebasing very differently from Windows NT. When Windows NT detects that a DLL needs to be loaded at an address different from its preferred load address, it maps the entire DLL as copy-on-write, fixes it up (causing all pages that contain fixups to be dumped into the page file), then restores the read-only/re...

History
Dec 15, 2004
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The hunt for a faster syscall trap

Raymond Chen

The performance of the syscall trap gets a lot of attention. I was reminded of a meeting that took place between Intel and Microsoft over fifteen years ago. (Sadly, I was not myself at this meeting, so the story is second-hand.) Since Microsoft is one of Intel's biggest customers, their representatives often visit Microsoft to show off what t...

History
Dec 14, 2004
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Why do dialog editors start assigning control IDs with 100?

Raymond Chen

When you use a dialog editor and insert new controls, they typically are assigned control IDs starting at around 100. Why? Because the small numbers are already taken. /* * Dialog Box Command IDs */ #define IDOK 1 #define IDCANCEL 2 #define IDABORT 3 #define IDRETRY 4 #define IDIGNORE ...

History
Dec 2, 2004
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Why did Windows 95 run the timer at 55ms?

Raymond Chen

The story behind the 55ms timer tick rate goes all the way back to the original IBM PC BIOS. The original IBM PC used a 1.19MHz crystal, and 65536 cycles at 1.19MHz equals approximately 55ms. (More accurately, it was more like 1.19318MHz and 54.92ms.) But that just pushes the question to another level. Why 1.19...MHz, then? With that clock rat...

History
Dec 1, 2004
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What is the purpose of the bmPlanes member of the BITMAP structure?

Raymond Chen

Many bitmap-related structures in Windows have a field called "planes". For example the structure has a member (which must be set to 1). The structure has a field called . What's the deal with that field? The EGA video adapter supported 16 simultaneous colors. This was an enormous improvement over the CGA, which supported only four colors. I...

History
Nov 22, 2004
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When people ask for security holes as features: World-writable files

Raymond Chen

If I had a nickel each time somebody asked for a feature that was a security hole... I'd have a lot of nickels. For example, "I want a file that all users can write to. My program will use it as a common database of goodies." This is a security hole. For a start, there's an obvious denial of service attack by having a user open the file in ...

HistoryWhen people ask for security holes as features