实验7

11-7

#include<iostream>
using namespace std;
int main()
{
ios_base::fmtflags original_flags=cout.flags(); //保存现在的参数设置
cout<<812<<'|';
cout.setf(ios_base::left,ios_base::adjustfield); //对齐方式为左对齐
cout.width(10); //设置输出宽度为10
cout<<813<<815<<'\n';
cout.unsetf(ios_base::adjustfield);
cout.precision(2);
cout.setf(ios_base::uppercase|ios_base::scientific); //以科学格式显示浮点数值并 显示大写字母E
cout<<831.0;
cout.flags(original_flags) //恢复原来的参数设置
return 0;
}

 11-3

#include<iostream>
#include<fstream>
using namespace std;
int main()
{
ofstream out("test1.txt");
out<<"已成功写入文件";
out.close() ;
return 0;
}

11-4

#include<iostream>
#include<fstream>
#include<string>
using namespace std;
int main()
{
string n;
ifstream in("test1.txt");
in>>n;
cout<<n;
in.close();
return 0;

}

 应用1

#include<iostream>
#include<fstream>
#include<cstdlib>
#include<ctime>
using namespace std;
struct student{
int num;
string xh,name,banji;
};
int main()
{
int i,n,g;
student pe[83];
ifstream in("list.txt");
if(!in)
{
cout<<"error";
return 0;
}
g=0;
while(in>>pe[g].num>>pe[g].xh>>pe[g].name>>pe[g].banji){
g++;
}
in.close();
ofstream out("roll.txt");
srand(time(NULL));
for(i=0;i<5;i++)
{
n=rand()%g+1;
out<<pe[n].num<<" "<<pe[n].xh<<" "<<pe[n].name<<" "<<pe[n].banji<<endl;
cout<<pe[n].num<<" "<<pe[n].xh<<" "<<pe[n].name<<" "<<pe[n].banji<<endl;
}
out.close();
return 0;
}

 

实验总结与体会

不知道为什么有时候文件读不出来，而且编出来的程序编译没问题但运行就出问题，检查了感觉又没错。’