Janet Jackson had the power to crash laptop computers - The Old New Thing
A colleague of mine shared a story from Windows XP product support. A major computer manufacturer discovered that playing the music video for Janet Jackson’s “Rhythm Nation” would crash certain models of laptops. I would not have wanted to be in the laboratory that they must have set up to investigate this problem. Not an artistic judgement. One discovery during the investigation is that playing t
Be careful with that thing, it's a confidential coffee maker - The Old New Thing
Raymond has been involved in the evolution of Windows for more than 30 years. In 2003, he began a Web site known as The Old New Thing which has grown in popularity far beyond his wildest imagination, a development which still gives him the heebie-jeebies. The Web site spawned a book, coincidentally also titled The Old New Thing (Addison Wesley 2007). He occasionally appears on the Windows Dev Docs
On finding the average of two unsigned integers without overflow - The Old New Thing
On finding the average of two unsigned integers without overflow Finding the average of two unsigned integers, rounding toward zero, sounds easy: unsigned average(unsigned a, unsigned b) { return (a + b) / 2; } However, this gives the wrong answer in the face of integer overflow: For example, if unsigned integers are 32 bits wide, then it says that average(0x80000000U, 0x80000000U) is zero. If you
On leading underscores and names reserved by the C and C++ languages - The Old New Thing
The C and C++ languages reserve certain categories of names for the implementation, which means that you cannot use them in your own code. Some are reserved unconditionally, precluding their use for variable names, parameter names, classes, methods, macros, whatever. Others are reserved only in certain contexts. The rules for C++ are collected in the [lex.name] chapter. The rules for C happen to m
Why did Windows 95 setup use three operating systems? - The Old New Thing
If you write Windows 95 setup as an MS-DOS app, then it runs on all three platforms. That’s great! You need to write only one setup program. The downside is that it’s going to be a text-mode setup program, which looks ugly and gives a poor initial impression of what is supposed to be a brand new GUI world. At the other extreme, you can write Windows 95 setup as a 32-bit GUI program, but that means
You can't copy code with memcpy; code is more complicated than that - The Old New Thing
Back in the day, a customer reported that their program crashed on Itanium. Wait, come back! Itanium is where the customer recognized the problem, but it applies to all other architectures, so stick with me. Their code went roughly like this: struct REMOTE_THREAD_INFO { int data1; int data2; int data3; }; static DWORD CALLBACK RemoteThreadProc(REMOTE_THREAD_INFO* info) { try { ... use the info to
How does Windows decide whether your computer has limited or full Internet access? - The Old New Thing
How does Windows decide whether your computer has limited or full Internet access? Windows lets you know when your computer’s Internet connection is limited or absent entirely. What is this sorcery? Windows attempts to download a file from a dedicated Web server. Depending on which version of Windows, it’s http://www.msftncsi.com/ncsi.txt or http://www.msftconnecttest.com/connecttest.txt. If the d
The x86 architecture is the weirdo - The Old New Thing
The x86 architecture does things that almost no other modern architecture does, but due to its overwhelming popularity, people think that the x86 way is the normal way and that everybody else is weird. Let’s get one thing straight: The x86 architecture is the weirdo. The x86 has a small number (8) of general-purpose registers; the other modern processors have far more. (PPC, MIPS, and Alpha each h
Why did Windows 95 use blue screen error messages instead of hard error messages? - The Old New Thing
Why did Windows 95 use blue screen error messages instead of hard error messages? Some time ago, I talked about the so-called hard error and what makes it harder than an easy error. The idea is that the “hard” error is used for low-level I/O errors that occur at unpredictable times, and which must be handled without allowing application code to run (because of the unpredictability). If the hard er
Now that computers have more than 4MB of memory, can we get seconds on the taskbar? - The Old New Thing
Now that computers have more than 4MB of memory, can we get seconds on the taskbar? The clock in the Windows taskbar does not display seconds. Originally, this was due to the performance impact on a 4MB system of having to keep in memory the code responsible for calculating the time and drawing it. But computers nowadays have lots more than 4MB of memory, so why not bring back the seconds? Althoug
What has case distinction but is neither uppercase nor lowercase? - The Old New Thing
If you go exploring the Unicode Standard, you may be surprised to find that there are some characters that have case distinction yet are themselves neither uppercase nor lowercase. Oooooh, spooky. In other words, it is a character c with the properties that toUpper(c) ≠ toLower(c), yet c ≠ toUpper(c) and c ≠ toLower(c). Congratulations, you found the mysterious third case: Title case. There are so
Why are there separate Program Files and Program Files (x86) directories? - The Old New Thing
Why are there separate Program Files and Program Files (x86) directories? On Windows editions that support x86 emulation, there are two directories for program files. The C:\Program Files directory is for programs in the native system bitness, and the the C:\Program Files (x86) directory is for programs that run under the x86-32 emulator. But why are they separate directories? Why can’t we combine
Is there a maximum size for Windows clipboard data? Because I'm getting null for something I know should be there - The Old New Thing
Is there a maximum size for Windows clipboard data? Because I’m getting null for something I know should be there A customer had a program that opened a very large spreadsheet in Excel. Very large, like over 300,000 rows. They then selected all of the rows in the very large spreadsheet, copied those rows to the clipboard, and then ran a program that tried to extract the data. The program used the
The inside story of the outside investigation of SoftRAM 95 - The Old New Thing
With the release of Windows 95 came quite a number of software products tailored to run on it. One of them that drew a lot of attention at the time was SoftRAM 95, a product whose box claimed it would “Double Your Memory”. It turns out that it didn’t. There are many write-ups of what the software did (and notably didn’t do), but almost none of them dug deep into the code to explain what it was doi
Why doesn't Windows use the 64-bit virtual address space below 0x00000000`7ffe0000? - The Old New Thing
Why doesn’t Windows use the 64-bit virtual address space below 0x00000000`7ffe0000? A customer used VMMap and observed that for all of their 64-bit processes, nothing was allocated at any addresses below 0x00000000`7ffe0000. Why does the virtual address space start at 0x00000000`7ffe0000? Is it to make it easier to catch pointer truncation bugs? And what’s so special about 0x00000000`7ffe0000? Oka
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