为什么十六进制数以 0x 为前缀? [英] Why are hexadecimal numbers prefixed with 0x?

问题描述

为什么十六进制数字的前缀为 0x?我了解前缀的用法，但我不明白为什么选择 0x 的意义.

Why are hexadecimal numbers prefixed as 0x? I understand the usage of the prefix but I don't understand the significance of why 0x was chosen.

推荐答案

Short story: 0 告诉解析器它正在处理一个常量(而不是一个标识符/保留字).仍然需要一些东西来指定基数:x 是一个任意选择.

Short story: The 0 tells the parser it's dealing with a constant (and not an identifier/reserved word). Something is still needed to specify the number base: the x is an arbitrary choice.

长话:在 60 年代，流行的编程数字系统是十进制和八进制——大型机每字节有 12、24 或 36 位，可以很好地整除3 = log2(8).

Long story: In the 60's, the prevalent programming number systems were decimal and octal — mainframes had 12, 24 or 36 bits per byte, which is nicely divisible by 3 = log2(8).

BCPL 语言使用语法 8 1234 表示八进制数.当 Ken Thompson 从 BCPL 创建 B 时，他使用了 0 前缀.这很棒，因为

The BCPL language used the syntax 8 1234 for octal numbers. When Ken Thompson created B from BCPL, he used the 0 prefix instead. This is great because

1. 一个整数常量现在总是由一个标记组成，
2. 解析器仍然可以立即判断它有一个常量，
3. 解析器可以立即告诉基数(0在两个基数中是相同的)，
4. 在数学上是合理的 (00005 == 05)，并且
5. 不需要珍贵的特殊字符(如#123).

1. an integer constant now always consists of a single token,
2. the parser can still tell right away it's got a constant,
3. the parser can immediately tell the base (0 is the same in both bases),
4. it's mathematically sane (00005 == 05), and
5. no precious special characters are needed (as in #123).

当从 B 创建 C 时，出现了对十六进制数的需求(PDP-11 有 16 位字)，并且上述所有要点仍然有效.由于其他机器仍然需要八进制，所以任意选择了 0x(00 可能被排除为笨拙).

When C was created from B, the need for hexadecimal numbers arose (the PDP-11 had 16-bit words) and all of the points above were still valid. Since octals were still needed for other machines, 0x was arbitrarily chosen (00 was probably ruled out as awkward).

C# 是 C 的后代，所以它继承了语法.

C# is a descendant of C, so it inherits the syntax.

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