![]() A DWORD in the Win32 API is 32 bits, and a QWORD is 64 bits. However, even when you compile code that contains this macro for a 32 bit or 64 bit target, it will still be 16 bits. This made sense when processors were 16 bit. In legacy Windows programming (the Win32 API), there is a macro defined called WORD, the size of which is 16 bits. The capitalization and the specific sizes in the question (16 bit for WORD, on a 32 bit OS) imply something different than the generic term "processor word". The question's specific context - WORD, in all-caps See the "processor word" wiki article I linked above, or an article about the specific system in question. Those tend to be talked about as "64 bit" or "8 bit" systems, but the truth is a bit more complicated than that. Note: This concept starts getting slightly more complicated when you talk about older and more specialized processors (especially older video game systems), but the question wasn't really about those so I won't go into detail. These concepts aren't strictly the same as the generic concept of a "processor word", but are closely related. This is because all the old CPU instructions still exist on new CPUs, and they are backwards compatible. It can do this without any changes to the code, and without having to rebuild the software. This means that instead of only being able to use a maximum of 4 Gigabytes of RAM (like "32 bit software"), it can theoretically use about 17 Billion Gigabytes of RAM (16 Exabytes).Ī "64 bit" 圆4/x86 CPU can also run "32 bit" (or even "16 bit") software. adding 64 bit numbers together, or copying 64 bits of data from a processor register to RAM at the same time). "64 bit software" uses 64 bit instructions (e.g. "Bit size" of software/OS vs the "bit size" of hardwareĪ "64 bit" CPU and a "64 bit" OS are necessary in order to run "64 bit" software. There is a wikipedia article on this "processor word" concept, which details all the generic uses of the term, and the sizes for several current and historical CPU architectures. ![]() A 64 bit processor will have a 64 bit "word" size (and pointer size). In simple cases, a 32 bit processor will have a 32 bit "word" size (and pointer size). It can also refer to the size of CPU instruction, or the size of a pointer (depending on which exact CPU architecture). In common/generic usage, a "processor word" refers to the size of a processor register. The generic term "processor word", in context of CPU architectures The Intel/AMD instruction set concept of a "Word", "Doubleword", and "Quadword".When describing the Win32 WORD type definition, this also comes up: ![]() The all-caps term WORD, meaning a 16 bit value - This is a part of the Windows "Win32" C language API.The "bit size" of software/OS, vs the "bit size" of hardware. ![]()
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