C++编程语言教程 - cplusplus.com

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"C++语言教程" 《C++ Language Tutorial》是一本专为C++初学者设计的学习资料，由Juan Soulié撰写，并在2007年6月进行了最后修订。该教程可在官方网站cplusplus.com上获取，且在线版本会持续更新，可能包含修正和新增内容。这份文档及其所有内容受Copyright © cplusplus.com, 2008保护，禁止未经许可的任何形式的分发、复制或修改（包括版权声明）。读者只能打印个人使用的完整文档副本或将文档下载到本地硬盘，不得修改其内容。未经cplusplus.com的书面许可，不得传播或以其他任何形式存储在任何网站或其他电子检索系统中。此教程的目录如下，提供了全面的学习路径： 1. **介绍**：这部分通常会涵盖C++语言的历史、重要性以及学习C++的基础知识，帮助新手了解C++的背景和应用领域，为后续学习奠定基础。 2. **指令使用**：这部分可能详细说明如何有效地使用教程，包括阅读指南、学习策略和推荐的学习顺序，以帮助读者更高效地掌握C++编程。尽管没有提供具体章节内容，但一个标准的C++教程通常会包含以下主题： - **基础语法**：变量、数据类型、运算符、控制流（如if语句、循环）、函数等。 - **类与对象**：面向对象编程的基础，包括类的定义、对象的创建、封装、继承和多态等概念。 - **模板**：学习如何创建和使用泛型代码，以提高代码的复用性和灵活性。 - **命名空间**：理解如何组织和避免命名冲突。 - **异常处理**：学习错误处理机制，包括try、catch和throw关键字。 - **输入/输出流**：I/O库的使用，包括cin和cout，以及文件操作。 - **标准库**：介绍STL（Standard Template Library），如容器（vector、list、set等）、迭代器、算法和函数对象等。 - **指针和内存管理**：理解指针的概念，动态内存分配和释放，以及引用。 - **预处理器**：涵盖宏定义和其他预处理指令。 - **高级话题**：可能包括多线程编程、模板元编程、C++11及更高版本的新特性等。通过这个详尽的教程，初学者可以逐步掌握C++编程语言的核心概念和技术，为成为一名熟练的C++程序员打下坚实基础。

A first difference with fundamental data types is that in order to declare and use objects (variables) of this type we

need to include an additional header file in our source code: <string> and have access to the std namespace

(which we already had in all our previous programs thanks to the using namespace statement).

// my first string

#include <iostream>

#include <string>

using namespace std;

int main ()

{

string mystring = "This is a string";

cout << mystring;

return 0;

}

This is a string

As you may see in the previous example, strings can be initialized with any valid string literal just like numerical

type variables can be initialized to any valid numerical literal. Both initialization formats are valid with strings:

string mystring = "This is a string";

string mystring ("This is a string");

Strings can also perform all the other basic operations that fundamental data types can, like being declared without

an initial value and being assigned values during execution:

// my first string

#include <iostream>

#include <string>

using namespace std;

int main ()

{

string mystring;

mystring = "This is the initial string content";

cout << mystring << endl;

mystring = "This is a different string content";

cout << mystring << endl;

return 0;

}

This is the initial string content

This is a different string content

For more details on C++ strings, you can have a look at the string class reference.

Constants

Constants are expressions with a fixed value.

Literals

Literals are used to express particular values within the source code of a program. We have already used these

previously to give concrete values to variables or to express messages we wanted our programs to print out, for

example, when we wrote:

a = 5;

the 5 in this piece of code was a literal constant.

Literal constants can be divided in Integer Numerals, Floating-Point Numerals, Characters, Strings and Boolean

Values.

Integer Numerals

1776

707

-273

They are numerical constants that identify integer decimal values. Notice that to express a numerical constant we

do not have to write quotes (") nor any special character. There is no doubt that it is a constant: whenever we

write 1776 in a program, we will be referring to the value 1776.

In addition to decimal numbers (those that all of us are used to use every day) C++ allows the use as literal

constants of octal numbers (base 8) and hexadecimal numbers (base 16). If we want to express an octal number

we have to precede it with a 0 (zero character). And in order to express a hexadecimal number we have to precede

it with the characters 0x (zero, x). For example, the following literal constants are all equivalent to each other:

75 // decimal

0113 // octal

0x4b

// hexadecimal

All of these represent the same number: 75 (seventy-five) expressed as a base-10 numeral, octal numeral and

hexadecimal numeral, respectively.

Literal constants, like variables, are considered to have a specific data type. By default, integer literals are of type

int. However, we can force them to either be unsigned by appending the u character to it, or long by appending l:

75 // int

75u // unsigned int

75l // long

75ul

// unsigned long

In both cases, the suffix can be specified using either upper or lowercase letters.

Floating Point Numbers

They express numbers with decimals and/or exponents. They can include either a decimal point, an e character

(that expresses "by ten at the Xth height", where X is an integer value that follows the e character), or both a

decimal point and an e character:

3.14159 // 3.14159

6.02e23 // 6.02 x 10^23

1.6e-19 // 1.6 x 10^-19

3.0 // 3.0

These are four valid numbers with decimals expressed in C++. The first number is PI, the second one is the

number of Avogadro, the third is the electric charge of an electron (an extremely small number) -all of them

approximated- and the last one is the number three expressed as a floating-point numeric literal.

The default type for floating point literals is double. If you explicitly want to express a float or long double

numerical literal, you can use the f or l suffixes respectively:

3.14159L // long double

6.02e23f // float

Any of the letters that can be part of a floating-point numerical constant (e, f, l) can be written using either lower

or uppercase letters without any difference in their meanings.

Character and string literals

There also exist non-numerical constants, like:

'z'

'p'

"Hello world"

"How do you do?"

The first two expressions represent single character constants, and the following two represent string literals

composed of several characters. Notice that to represent a single character we enclose it between single quotes (')

and to express a string (which generally consists of more than one character) we enclose it between double quotes

(").

When writing both single character and string literals, it is necessary to put the quotation marks surrounding them

to distinguish them from possible variable identifiers or reserved keywords. Notice the difference between these

two expressions:

'x'

x alone would refer to a variable whose identifier is x, whereas 'x' (enclosed within single quotation marks) would

refer to the character constant 'x'.

Character and string literals have certain peculiarities, like the escape codes. These are special characters that are

difficult or impossible to express otherwise in the source code of a program, like newline (\n) or tab (\t). All of

them are preceded by a backslash (\). Here you have a list of some of such escape codes:

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