Types

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不管什么数在计算机里都是二进制的数, 重点是我们怎么看他, 体现了不同的数据类型 —— 翁恺

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A type defines both the contents of a data element and the operations that are possible on those data. (C++ Primer, p32)

（class也是这个味道吧）

可以用这个 🔗sizeof 来计算一个 type 占据了多少空间。

Machine-Level Representation of the Built-in Types

• The smallest chunk of addressable memory is referred to as a “byte”

• a small number of bytes, is referred to as a “word”

• In C++ a byte has at least to hold a character in the machine’s basic character set

• Most computers associate address with each byte in memory.

• The type determines how many bits are used and how to interpret those bits

• type 决定了这个地址上的 object span 了多少 memory. 所以说是这样一个 byte？还是那样一个 word？

Primitive Built-in Types

include the arithmetic types and a special type named void.

the arithmetic types represent characters, integers, boolean values, and floating-point numbers.

Arithemtic Types

this types are divided into: 🔗Integral Types and 🔗Floating-point Types. (对照前文判断一下谁是整数型，谁是浮点型)

for integral types, there exsist 🔗Signed and Unsigned Types

Compound Types

A compound type is a type that is defined in terms of another type.

🔗References and 🔗Pointers are two compound types. They are similar in some circumstance.
🔗Arrays is also a compound type.

compound compound types

when the two compound “refrence to pointers”, we read the definition right to left.

int *&r = p;    // r is a reference to the pointer p

the first modifier & indicates r is a reference, and the specifier int* says r is refer to a pointer.

Literals

Type Conversions

const and Constant Expressions

Type Aliases

🌟Type Specifiers

Library Types

type	template
🔗string	🔗vector
	🔗initializer_list