Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
113 views
in Technique[技术] by (71.8m points)

c++ - System where 1 byte != 8 bit?


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

On older machines, codes smaller than 8 bits were fairly common, but most of those have been dead and gone for years now.

C and C++ have mandated a minimum of 8 bits for char, at least as far back as the C89 standard. [Edit: For example, C90, §5.2.4.2.1 requires CHAR_BIT >= 8 and UCHAR_MAX >= 255. C89 uses a different section number (I believe that would be §2.2.4.2.1) but identical content]. They treat "char" and "byte" as essentially synonymous [Edit: for example, CHAR_BIT is described as: "number of bits for the smallest object that is not a bitfield (byte)".]

There are, however, current machines (mostly DSPs) where the smallest type is larger than 8 bits -- a minimum of 12, 14, or even 16 bits is fairly common. Windows CE does roughly the same: its smallest type (at least with Microsoft's compiler) is 16 bits. They do not, however, treat a char as 16 bits -- instead they take the (non-conforming) approach of simply not supporting a type named char at all.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...