C++ Primer(英语第5版) 阅读日记 - 20200412

接上篇。晚上看书，效率倍加倍。

Chapter 2. Variables and Basic Types

Arithmetic types: 

• characters
• integers
• boolean values
• floating-point variables

Void type: void type has no associated values and could be used in only a few circumstances, most commonly as the return type for functions that do not return a value.

Arithmetic types 通常分为两类：intergral types（应该翻译做整型，包括char和boolean）还有 floating-point types （浮点型，很好理解是小时嘛）。

常用类型的大小：

类型	变量大小
char	1 byte
short	2 bytes
int	2 bytes
long	4 bytes
long long	8 bytes
float	4 bytes (typically)
double	8 bytes (typically)

extended character types： char16_t, char32_t 是为Unicode字符设计的，所以更加大。关于Unicode和Utf-8, GBK关系我又忘了，改天梳理一下。这里留个坑，以后链接到这里。

Signed and unsigned types

除了bool和extended character types，intergral types都应该是有符号的：signed或者unsigned。

如果我们强行分配超出范围的值给一个变量，会发生什么？

• 如果是unsigned的整型，多余的bit会被直接切掉
• 如果是signed整型的话，结果就会undefined。意味着乱码，崩溃等有可能发生。而且compiler可能不报错。

Literals

A value, such as 42, is known as a literal because its value self-evident. Every literal has a type.