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In Microsoft C, you can initialize the values of an entire bitfield structure as an integer in several ways:
In Microsoft C, bitfields are stored in word-sized blocks with the least significant bit representing the first bit of the bitfield. For example, the bitfields in bitstruct, defined below in the example, are stored as follows:
Assigning the integer 0x4c to this structure results in the following bit pattern:
< p4 > < p3 > < p2> <p1> |?|?|?|?|?|?|?|?|?|?|?|?|?|?|?|?|
The bitfields are given the following respective values:
If the number of bits needed for a bitfield structure exceeds 16 in code compiled for MS-DOS or Windows, words will be added as needed to provide room for the structure with no single bitfield crossing a word boundary. Microsoft C/C++, 32-bit Edition, stores bitfield structures in double word values. If the field requires more than 32 bits, the compiler uses additional double words as needed.
p1=0 p2=3 p3=2 p4=0
NOTE: There is no "standard" for storing bitfields in memory; therefore, any program that depends on a particular storage method is not portable to systems that use a different method.
Article ID: 60252 - Last Review: February 27, 2014 - Revision: 2.1
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