1 and Windows NT 3.x, each key had only
one value. Starting in Windows 95, a key could contain any number of values; the default value
simply took the place of the lone value from previous versions, allowing compatibility with older
applications that were written before the change took effect. In fact, many things you??™ll find in the
Registry are designed with such ???legacy??? support in mind.
The Structure of the Registry | 93
The Registry
value, apart from what might have been assigned by the programmer of the
particular application that uses the key.
When Is a Number Not Just a Number?
Sometimes the number stored in a DWORD value is actually made up of several
components, all glued together with the binary arithmetic we were supposed
to have learned in the seventh grade.
The term ???DWORD??? is an abbreviation for ???Double Word,??? which means
that it can store two 16-bit values (known as ???Words??? in geekspeak). A 16-bit
value is basically a whole number (integer) that can be stored in 16 bits, which
means it can be no larger than 216, or 65,536. So, aDWORDvalue can be used
to store two of these, or one 32-bit number (up to 232, or 4,294,967,296), or
even thirty-two 1-bit numbers (each of which can be 1 or 0).
Windows Vista also supports the 64-bit DWORD value, which is available
even if you??™re using the 32-bit edition of Vista. A 64-bit DWORD??”equivalent
to aQWORD(Quadruple Word)??”can hold sixty-four 1-bit values, four
16-bit values, two 32-bit values, or one 64-bit value (which can be up to about
1.
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