qword, instead of __int64
Author
I am reading an assembly programming book, and I just knew that in addition to dword, there is qword (quad word). word is 2 bytes, and is commonly associated with short. dword is 4 bytes, associated with long. qword is 8 bytes, but I never see it as a data type?
word/dword/qword are ASM datatypes. They are not officially defined in the C/C++ standard (the fact that MS uses them in the windows header files is another thing). QWORD is the ASM counterpart of __int64, and is commonly used in FPU code. You can always typedef qword to __int64, if you want.
[edited by - Yann L on May 7, 2003 2:09:43 PM]
[edited by - Yann L on May 7, 2003 2:09:43 PM]
Author
Right. I can typedef it, but what I don''t understand is the fact that DWORD is widely used while QWORD is not.
QWORD isn''t used very much for two reasons.
1. You generaly don''t need a variable that large
2. Most of todays processors are 32bit NOT 64bit so QWORDs aren''t directly supported which makes them alot slower than using standard DWORDs
1. You generaly don''t need a variable that large
2. Most of todays processors are 32bit NOT 64bit so QWORDs aren''t directly supported which makes them alot slower than using standard DWORDs
Also, I''ll bet if you want to use them (like simply printing one out) you''d have to write your own printing method.
Is there an already-written output function which accepts int64?
Is there an already-written output function which accepts int64?
Again: WORD/DWORD & co. are not C/C++ types. They are ASM types, and QWORD is commonly used in ASM code. Microsoft happened to use those ASM types in C/C++, but that's about all. They could also have named them MS_short, MS_int, or Bill_Gates_int64. It was just a convenience typedef, to get machine independent types (there were DEC Alpha + MIPS versions of Win NT, not only x86).
Uh, printf() or iostream ?
[edited by - Yann L on May 7, 2003 7:33:59 PM]
quote:
Is there an already-written output function which accepts int64?
Uh, printf() or iostream ?
[edited by - Yann L on May 7, 2003 7:33:59 PM]
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