C++输入输出流的一些基础类方法

#include<iostream>
#include<iomanip>
#include<cstdlib>
#include<string>
#include<cstring>
#include<cmath>
#include<cctype>
#include<exception>
#include"windows.h"

using namespace std;
int main()
{
	char *ch = "china";
	cout << "Address:"<<(void *)ch << endl;//要获取字符串的地址可以用void *强制转换
	cout.put(ch[1]).put(ch[2])<<"***put()\n";//用put()输出一个字符
	cout.write(ch,strlen(ch))<<"**write()\n"<<flush;//用write()输出一个字符串
	int n = 12;
	cout  <<dec<< n << "="<<oct<<n<<"="<<hex<<n<<endl;//或者利用hex(cout);
	string str[][4] = { { "January", "Feburary", "March", "April" }, { "May", "June", "July", "August" }
	, { "September", "Octomber", "November", "December" } };
	int init_width = cout.width();//返回初始宽度
	ios_base::fmtflags init_style = cout.setf(ios_base::left, ios_base::adjustfield);
	ios_base::fmtflags init_decimal = cout.setf(ios_base::dec, ios_base::basefield);
	ios_base::fmtflags init_float = cout.setf(ios_base::fixed, ios_base::floatfield);
	for (int i = 0; i < 3; i++)
	{
		for (int j = 0; j < 4; j++)
		{
			//cout.width(12);
			cout.fill(' ');
			cout << "|"<<setw(12)<<str[i][j];
		}
		cout << "|";
		cout << endl;
	}
	double x = 3.14;
	cout.precision(3);//默认格式下是最终结果的位数，对于科学计数法和定点表示法中它是小数点后位数
	cout << "sqrt(3.14)=" << sqrt(x) << endl;
	cout.setf(ios_base::showpoint);
	//showpoint,boolalpha,showbase,uppercase,showpos均是类ios_base中定义的常数
	cout << "6.0/3=" << 6.0/3 << endl;
	cout.setf(init_style, ios_base::adjustfield);
	cout.setf(init_float, ios_base::floatfield);
	cout << "sqrt(3.14)=|";
	cout.width(12);
	cout.precision(10);
	cout.setf(ios_base::showpos);
	cout<< sqrt(x) << endl;
	cout.unsetf(ios_base::showpos);
	cout << sqrt(x) << endl;
	cout << setw(10) << setprecision(8) << setfill('*') << sqrt(2) << endl;
	int num,sum=0;
	cin.exceptions(ios_base::failbit);
	cout << "please input a num:";
	try{
		while (cin >> num)
		{
			sum += num;
		}
	}
	catch (ios_base::failure &f)
	{
		cout << f.what() << endl;
		cout << "This is a horror.\n";
	}
	cout << "The last input is:" << num << endl;
	cout << "Sum=" << sum << endl;
	if (!cin.eof()&&cin.fail())//读取失败因为数据不匹配
	{ 
		cin.clear();
		while (!isspace(cin.get()))  //读取下一个数据
			continue;
		int next;
		cin >> next;
		cout << "The next number is: " << next << endl;
		while (cin.get() != '\n')  //清空输入
			continue;
	}
	else
	{
		cout << "Sorry,I can't go on.\n";
		exit(0);
	}
	cout << "Let's to test cin about char.\n";
	int count = 0;
	char c;
	cin>>c;
	while (c != '#')//不能采用'\n'来作为输入结束的标识，因为cin>>会自动跳过空格，换行符和回车
	{
		cout << c;
		count++;
		cin >> c;
	}
	cout << "\ncount=" << count << endl;
	while (cin.get() != '\n')  //清空输入
		continue;
	count = 0;
	while (cin.get(c))//读取到文件尾，windows可以利用ctrl+Z模拟文件尾输入
	{
		if (c == '\n') break;
		cout << c;
		count++;
	}
	cout << "\ncount=" << count << endl;
	count = 0;
	char ch1;
	ch1= cin.get(); //cin.get()返回值是int型
	while (ch1 != '\n')
	{
		cout << ch1;
		count++;
		ch1 = cin.get();
	}
	cout << "\ncount=" << count << endl;
	int ch2;
	while ((ch2 = cin.get()) != EOF)
	{
		if (ch2 == '\n') break;
		cout << ch2;
	}
	cout << "\nDone!\n";
	char s[20];
	cout << "please input a string.\n";
	cin.getline(s, 20, '#');//getline()丢弃标志符'#'
	char nex1 = cin.get();
	cout << "String: " << s << ",Next char: " << nex1 << endl;
	cout << "please input another string.\n";
	cin.get(s, 20, '#');//get()保留标志符'#'
	char nex2 = cin.get();
	cout << "String: " << s << ",Next char: " << nex2 << endl;
	cin.ignore(20, '\n');//ignore()一般用来丢弃剩下的输入流中字符
	char flag;
	cin >> flag;
	cout << "flag=" << flag << endl;
	if (cin.peek()!='\n')//peek()用来查看下一个字符并返回它，并不取出输入流的数据
		cin.ignore(20, '\n');
	//read()创建的字符串并不自动在末尾加'\0'，putback()将一个字符加到输入流中
  system("pause");
  return 0;
}

程序运行结果如下