Article: Q40027
Product(s): Microsoft C Compiler
Version(s): 1.0,1.5,1.51,1.52,2.0,2.1,4.0,5.0,6.0
Operating System(s):
Keyword(s): kbLangC kbVC100 kbVC150 kbVC151 kbVC152 kbVC200 kbVC210 kbVC400 kbVC500 kbVC600
Last Modified: 29-NOV-2001
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The information in this article applies to:
- Microsoft C for MS-DOS
- Microsoft C/C++ for MS-DOS
- Microsoft Visual C++, versions 1.0, 1.5, 1.51, 1.52, 2.0, 2.1, 4.0
- Microsoft Visual C++, 32-bit Enterprise Edition, versions 5.0, 6.0
- Microsoft Visual C++, 32-bit Professional Edition, versions 5.0, 6.0
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0
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SUMMARY
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The pack pragma affects declarations, not definitions. Place #pragma pack()
prior to data declarations.
MORE INFORMATION
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Sample Code
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The following program demonstrates usage of #pragma pack():
/* compile options needed */
/* Elements of variables of type struct x will be byte-aligned. */
#pragma pack(1)
struct x { int a; char b; int c; };
/* Elements of variables of type struct y will be word-aligned. */
#pragma pack(2)
struct y { int a; char b; int d; };
/* The pragma below does NOT affect the definitions that follow. */
#pragma pack(4)
struct x X;
struct y Y;
void main (void)
{ /* dummy main */ }
NOTE: The default packing value for the 16-bit products mentioned above is 2
bytes. The default packing value for Visual C++ 32-bit, versions 1.0 and 2.xx,
is 4 bytes. The default packing value for Visual C++ 32-bit, version 4.0, is 4
bytes for bit fields and 8 bytes otherwise.
Additional query words:
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Keywords : kbLangC kbVC100 kbVC150 kbVC151 kbVC152 kbVC200 kbVC210 kbVC400 kbVC500 kbVC600
Technology : kbVCsearch kbVC400 kbAudDeveloper kbZNotKeyword8 kbvc150 kbvc100 kbCCompSearch kbZNotKeyword3 kbVC500 kbVC600 kbVC151 kbVC200 kbVC210 kbVC32bitSearch kbVC152 kbVC500Search
Version : :1.0,1.5,1.51,1.52,2.0,2.1,4.0,5.0,6.0
Issue type : kbinfo
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