Einstein discovered that simultaneity is relative. This is also true of computing. People will ask, "Is it okay to do X on one thread and Y on another thread simultaneously?" Here are some examples: You can answer this question knowing nothing about the internal behavior of those operations. All you need to know are some physics and the ...
Even though Windows NT uses UTC internally, the BIOS clock stays on local time. Why is that? There are a few reasons. One is a chain of backwards compatibility. In the early days, people often dual-booted between Windows NT and MS-DOS/Windows 3.1. MS-DOS and Windows 3.1 operate on local time, so Windows NT followed sui...
For some reason, some people go to enormous lengths to locate the Internet Explorer binary so they can launch it with some options. The way to do this is not to do it. If you just pass "IEXPLORE.EXE" to the ShellExecute function [link fixed 9:41am], it will go find Internet Explorer and run it. ShellExecute(NULL, "open", "iexplore.exe", ...
In an earlier article, I gave an example of reading a contract from the other side. Here's another example of how you can read a specification and play the role of the operating system. I chose this particular example because somebody wanted to do this and didn't realize that everything they needed was already documented; they just needed to look...
The various Interlocked functions (InterlockedIncrement, and so on) require that the variable being updated be properly aligned, even on x86, a platform where the CPU silently fixes unaligned memory access invisibly. If you pass an unaligned pointer to one of the Interlocked functions, the operation will still succeed, but the result won't be ato...
It has become obvious by now that the mobile phone has changed the way people interact. These two papers were forwaded to me by a colleague, whose summary I am shamelessly lifting from heavily. First is a short paper titled Exploring the implications for social identity of the new sociology of the mobile phone. The much more fascinating (and ...
Sometimes unaligned memory access will hang the machine. Some video cards do not let you access all the video memory at one go. Instead, you are given a window into which you can select which subset of video memory ("bank") you want to see. For example, the EGA video card had 256K of memory, split into four 64K banks. If you wanted to access memo...
Some Windows structures are variable-sized, beginning with a fixed header, followed by a variable-sized array. When these structures are declared, they often declare an array of size 1 where the variable-sized array should be. For example: typedef struct _TOKEN_GROUPS { DWORD GroupCount; SID_AND_ATTRIBUTES Groups[ANYSIZE_ARRAY]; } TOKEN...
The FILETIME structure represents a 64-bit value in two parts: typedef struct _FILETIME { DWORD dwLowDateTime; DWORD dwHighDateTime; } FILETIME, *PFILETIME; You may be tempted to take the entire FILETIME structure and access it directly as if it were an __int64. After all, its memory layout exactly matches that of a 64-bit (little-endian)...
Even though a value is stored in the registry as REG_SZ, this doesn't mean that the value actually ends with a proper null terminator. At the bottom, the registry is just a hierarchically-organized name/value database. And you can lie and get away with it. Lots of people lie about their registry data. You'll find lots of things that should be...
