1.2. 初窥输入/输出

Exercise 1.3: Write a program to print "Hello, World" on the standard output.

编一个程序，在标准输出上打印“Hello, World”。

int main(void){cout << "Hello,world" << endl;return 0;}

Exercise 1.4: Our program used the built-in addition operator, +, to generate the sum of two numbers. Write a program that uses the multiplication operator, *, to generate the product of two numbers.我们的程序利用内置的加法操作符“+”来产生两个数的和。编写程序，使用乘法操作符“*”产生两个数的积。 #include <iostream>using namespace std;int main(void){int val1 = 0,val2 = 0;cout << "Please input two numbers:";cin >> val1 >> val2;cout << val1 << "*" << val2 << " = " << val1*val2 << endl;return 0;}Exercise 1.6: Explain what the following program fragment does:解释下面的程序段：   std::cout << "The sum of " << v1;             << " and " << v2;             << " is " << v1 + v2             << std::endl;Is this code legal? If so, why? If not, why not?这段代码合法吗？如果合法，为什么？如果不合法，又为什么？ 答：非法。因为1，2,4句有分号，形成单独的一句。234没有左操作数。