C#中char类型的大小

Question

只是想知道为什么我们在 C# (.NET) 中有 2 个字节大小的char类型，而不像其他编程语言中的 1 个字节？

Answer 1

A char is unicode in C#, therefore the number of possible characters exceeds 255. So you'll need two bytes.

Extended ASCII for example has a 255-char set, and can therefore be stored in one single byte. That's also the whole purpose of the System.Text.Encoding namespace, as different systems can have different charsets, and char sizes. C# can therefore handle one/four/etc. char bytes, but Unicode UTF-16 is default.

Answer 2

I'm guessing with “other programming languages” you mean C. C has actually two different char types: char and wchar_t . char may be one byte long, wchar_t not necessarily.

In C# (and .NET) for that matter, all character strings are encoded as Unicode in UTF-16. That's why a char in .NET represents a single UTF-16 code unit which may be a code point or half of a surrogate pair (not actually a character, then).

Answer 3

Actually C#, or more accurately the CLR's, size of char is consistent with most other managed languages. Managed languages, like Java, tend to be newer and have items like unicode support built in from the ground up. The natural extension of supporting unicode strings is to have unicode char's.

Older languages like C/C++ started in ASCII only and only later added unicode support.

Answer 4

因为 .NET 中的字符串被编码为 2 字节 Unicode 字符。

Answer 5

因为 C# 字符串中的字符默认为 Unicode 的 UTF-16 编码，即 2 个字节（默认情况下）。

Answer 6

C# using 16 bit character width probably has more to do with performance rather than anything else.

Firstly if you use UTF-8 you can fit every character in the "right" amount of space. This is because UTF-8 is variable width. ASCII chars will use 8 bits while larger characters will use more.

But variable length character encoding encourages a O(n) algorithm complexity in common scenarios. Eg Retrieving a character at a particular location in a string. There have been public discussions on this point. But the simplest solution is to continue using a character width that fits most of your charset, truncating the others. Now you have a fixed character width.

Strictly speaking, UTF-16 is also a variable width encoding, so C# ( and Java for that matter ) are using something of a hybrid since their character widths are never 32 bits.