C++编程语言教程 - cplusplus.com官方指南

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"C++英文版教程，由Juan Soulié撰写，最后修订于2007年6月，可在cplusplus.com上找到。" 这篇文档是C++编程语言的一个教程，由Juan Soulié编著，并在2007年6月进行了最后一次修订。它可以在官方网站c++programming.com上获取到最新的版本。此教程覆盖了C++语言的基础和高级概念，旨在帮助学习者理解和掌握C++编程。由于在线版本会持续更新，可能会包含修正和新增内容，所以建议访问官方网站以获取最准确的信息。 C++是一种强大的、通用的编程语言，它结合了过程化编程、面向对象编程以及泛型编程的特点。它是在C语言的基础上发展起来的，增加了类、模板、异常处理等特性，使得代码更加模块化，提高了软件开发的效率和可维护性。教程内容通常包括以下几个部分： 1. **基础**：介绍C++的基本语法，如变量、数据类型、运算符、控制结构（如if语句、循环）、函数等。 2. **面向对象编程**：涵盖类和对象的概念，继承、多态和封装等面向对象编程的核心原则。 3. **模板**：讲解如何使用模板来实现泛型编程，以提高代码的重用性。 4. **内存管理**：包括动态内存分配、指针的使用，以及防止内存泄漏的方法。 5. **输入/输出**：介绍如何使用iostream库进行标准输入输出，包括cin和cout的使用。 6. **异常处理**：学习如何在程序中捕获和处理错误，以增强程序的健壮性。 7. **预处理器**：讨论宏定义和其他预处理指令的作用。 8. **标准库**：介绍C++标准库中的各种容器（如vector、list、map）和其他实用工具。 9. **高级主题**：可能包括STL（标准模板库）、多线程编程、命名空间、模板元编程等。请注意，根据版权规定，个人可以打印整个文档或将其下载至本地硬盘，但不得修改内容，包括版权声明。未经cplusplus.com的明确书面许可，不得分发此文档的内容，也不能将内容存储在其他网站或任何形式的电子检索系统中。这确保了教程的原创性和完整性，同时也保护了作者和网站的权益。这个C++教程是学习者深入理解C++语言的重要资源，无论你是初学者还是有一定经验的程序员，都可以从中受益。通过系统的阅读和实践，你将能够掌握C++的精髓，从而更好地利用这一强大工具进行软件开发。

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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