C++入门教程：cplusplus.com在线指南

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"这是一本由Juan Soulié编写的C++语言教程，最新修订于2007年6月，可以在cplusplus.com上找到。该在线版本会不断更新，可能包含修正和变动。教程覆盖了C++的基础知识，并对版权有严格规定，禁止未经授权的复制、分发或修改内容。此外，提供了目录以方便查阅。" C++是一种强大且灵活的编程语言，广泛应用于系统软件、应用软件、游戏开发、驱动程序以及嵌入式系统等多个领域。这本书作为C++的国外教科书，特别适合国内的学习者，因其内容通常具有清晰的解释和丰富的实例，有助于理解和掌握C++的核心概念。教程的介绍部分可能会涵盖C++语言的历史、特点以及它与C语言的关系。C++是在C语言的基础上发展起来的，增加了类、模板、异常处理等面向对象特性，同时支持函数多态和泛型编程，使其成为一个功能强大的现代编程语言。在"Instructions for use"章节，作者可能会提供如何有效地学习和使用教程的指导，比如建议读者先从基础语法开始，然后逐步深入到高级主题，如内存管理、STL（标准模板库）、设计模式等。学习C++时，实践是至关重要的，因此教程可能包含大量示例代码供读者编写和运行，以加深理解。 C++语言的基础知识点包括： 1. 基本数据类型：如整型、浮点型、字符型等。 2. 变量声明与初始化：理解变量的作用域和生命周期。 3. 运算符：包括算术运算符、比较运算符、逻辑运算符等。 4. 控制结构：如条件语句（if, switch）、循环（for, while, do-while）和跳转语句（break, continue）。 5. 函数：定义、调用、参数传递和返回值。 6. 面向对象编程：类的定义、对象创建、继承、封装、多态性。 7. 异常处理：try-catch机制用于错误处理。 8. 内存管理：动态内存分配与释放（new, delete）。 9. 模板：用于实现泛型编程，提高代码复用性。 10. 预处理器：宏定义和头文件包含等。学习C++的过程中，理解并熟练掌握这些基础知识是至关重要的，同时，通过实际项目练习，可以更好地提升编程技能和问题解决能力。此外，随着C++标准的不断演进，如C++11、C++14、C++17、C++20等，教程也可能涉及这些新特性的介绍，帮助学习者与时俱进。

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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.

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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:

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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 than 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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