In the four years since the first public demonstration of 64-bit Windows in 1999, the OS has been fully ported and now runs native Itanium instructions for both the kernel and supporting processes. The LLP64 Windows pointer model (int and long remain 32 bits wide, "long long" and pointers are defined as 64 bits wide) provided for minimal code changes during the port. With the exception of architectural specific design in the kernel (some examples in table below), 32-bit and 64-bit Windows share common source code. For example, the Windows user interface remains the same. All the familiar Windows tools from Microsoft Notepad to Microsoft Internet Explorer can be produced in 32-bit or 64-bit images. The same holds true for application development: 32-bit code and 64-bit code can share common source.
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