c18_01.cpp

it can help you use C++ program we

#include <iostream >
#include <iomanip >
using namespace std;

int main()
{
	double average = 22.0/7;
	cout << average <<endl;
	cout << setprecision(3) << average <<endl;  
	//设置显示的小数的总位数为3位, 输出为3.14

	cout << setiosflags(ios::scientific) << setprecision(5)<< average <<endl;
	//setiosflags(ios::scientific)和setprecision(5)合用，
	//用于控制指数形式输出时，小//数点后的显示位数为5位，
	//输出为3．14286e + 000

	cout << setprecision(6);
	//重新恢复为系统的默认设置

	return 0;
}