C++ 入门

1. C++ 文件的后缀

   • .cc, .cxx, .cpp, .cp, .c

2. 通过命令行编译程序

1. 编写文件 prog1.cc
int main()
{
    return 0;
}

2. 执行命令:
CC prog1.cc
或者:
g++ -o prog1 prog1.cc

3. 运行生成的文件
    Linux 系统生成 a.out
    Windows 系统生成 prog1.exe
./a.out

4. 获取执行结果
echo $?

3. 输入/输出流
   • iostream
     • istream: 输入流;
       • cin: 标准输入流;
     • ostream: 输出流;
       • cout: 标准输出流;
       • cerr: 打印错误信息,用于处理 warning, error;
       • clog: 打印一般信息;

// 用户输入两个值,计算这两个值的和
#include <iostream>
/*
 * sum function:
 * Read two numbers and write their sum
 */
int main()
{
    // prompt user to enter two numbers
    std::cout << "Enter two numbers:" << std::endl;
    int v1 = 0, v2 = 0;
    std::cin >> v1 >> v2;
    std::cout << "The sum of " << v1 << " and " << v2
              << " is " << v1 + v2 << std::endl;
    return 0;
}

4.条件控制

// 需求: 将1至10之间的数累加

// === while 循环
#include <iostream>

int main()
{
    int sum = 0, val = 1;
    while (val <= 10) {
        sum += val;
        ++val;
    }
    std::cout << "Sum of 1 to 10 inclusive is "
              << sum << std::endl;

    return 0;
}

// === for 循环
#include <iostream>

int main()
{
    int sum = 0;
    for (int val = 1; val <= 10; ++val)
        sum += val;
    std::cout << "Sum of 1 to 10 inclusive is "
              << sum << std::endl;
    return 0;
}

**参考资料:** - [C++ Primer](https://book.douban.com/subject/10505113/)