include <iostream>

include <fstream>

include <iomanip>

include <string>

using namespace std;
class WF
{
int i;
char f;
public:
WF(int i,char f) :i(i),f(f){}

friend ostream& operator<<(ostream& os,WF o)
{
os.width(o.i);
os.fill(o.f);
return os;
}
};
int main()
{
cout.width(10);//fill ten bytes screen.
cout << 123 << endl;//width only used next time//宽度填充仅对下一次输出有效
cout << 123 << endl;
cout.width(1); //fill one byte screen
cout << 123 << endl;
cout.width(10);
cout.fill(''); //free space used of ‘’.often used ..until the end of the program
cout <<123<<endl;
cout.width(10);
cout << 123 << endl;
cout.precision(8);//set precision //设置精度
cout << (double)123.0 <<endl;
//often see output control sign
cout.setf(ios::left); //left 向左对齐

cout.setf(ios:: right | ios::showpos);
cout.setf(ios::scientific | ios::uppercase);
cout << WF(8,'') << 123 <<endl;
cout.unsetf(ios::scientific | ios::uppercase);
cout.unsetf(ios:: right | ios::showpos);
//====================================
cout << setw(10) << setfill('~') << left << 123 << endl;
cout << setw(10) << setfill('+') << right << 123 << endl;
//================================
string str;
str = "hello";
cout << sizeof(str) <<endl;
str = "hello,world!";
cout << sizeof(str) <<endl; //输出结果一样，sizeof只注重类型，不关注内容。。是指针
//ofstream fout("app.txt",ios::app);//add to the file end//追加在文件后面 //顺序读写方法
//seekg（位置 int）跳着读写方法
//getline(cin,str);
ofstream fout("seek.txt",ios::out | ios::binary);
fout << "hello,sd0705!" <<endl;
fout.seekp(0);//first write H
fout.put('H');
fout.seekp(7);
fout <<"S";
fout << str << endl;
fout.close();
/
ios::right //右对齐
/========
ios::dec
ios::oct
ios::hex
/========
ios::showbase// take prefix output 带着前缀输出
ios::showpoint //take point output 带着小数点输出
ios::scientific //science output 科学输入法输出 3.5 e 9
ios::uppercase // uppercase 大写输出
ios::showpos// use sign output //使用符号输出
ios::app //start writing at end of file
ios::ate //start reading or writing at end of file
ios::in //open for reading
ios::trunc //truncate file to zero length if exists
ios::nocreate //erroe when opening if file does not exist
ios::noreplace :error when opening for output if file exist
ios::binary //open file in binary mode
ios::out //open for writing
/=======
//flush ：clear out buffer
endl: insert a '\n' and clear out buffer
oct:set the output as oct
dec
hex
{
setw(宽度)
setfill(填充字符)
setprecision(精度)
必须有头文件 <iomanip>
}
/
//cout.left
//=======================after revision
/char ch;
int num;
cout << "cin num and char" << endl;
cin >> num >> ch;
cout << WF(num,ch) << 123 <<endl; //must have output //必须有输出
*/