十年的生信

#文本文件

#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    int a[10],max,i,order;
    ifstream infile("f1.dat",ios::in);
    {
        cout << "open error !" << endl;
        exit(1);
    }
    for (i=0;i<10;i++)
    {
        infile >> a[i];
        cout << a[i] << " ";
    }
    cout << endl;
    max=a[0];
    order=0;
    for (i=1;i<10;i++)
    {
        if(a[i]>max)
        {
            max=a[i];
            order=i;
        }
    }
    cout << "max=" << max << endl << "order=" << order << endl;
    infile.close();

    return 0;
} 

#二进制文件

#include <fstream>
#include <iostream>

using namespace std;

struct student
{
    int num;
    char name[20];
    float score;
};

int main()
{
    student stud[5]={1001,"Li",85,1002,"Fun",97.5,1004,"Wang",54,1006,"Tan",75.6,1010,"ling",96};
    fstream iofile("stud.dat",ios::in|ios::out|ios::binary);
    if(!iofile)
    {
        cerr << "open error !" << endl;
        abort();
    }
    for(int i=0;i<5;i++)
        iofile.write((char*)&stud[i],sizeof(stud[i]));
    student stud1[5];
    for (int i=0;i<5;i=i+2)
    {
        iofile.seekg(i*sizeof(stud1[i]),ios::beg);
        iofile.read((char*)&stud1[i/2],sizeof(stud1[i/2]));
        cout << stud1[i/2].num << " " << stud1[i/2].name << " " << stud1[i/2].score << endl;
    }
    cout << endl;
    stud[2].num=1012;
    strcpy(stud[2].name,"Wu");
    stud[2].score=60;
    iofile.seekp(2*sizeof(stud[0]),ios::beg);
    iofile.write((char*)&stud[2],sizeof(stud[2]));
    iofile.seekg(0,ios::beg);
    for(int i=0;i<5;i++)
    {
        iofile.read((char*)&stud[i],sizeof(stud[i]));
        cout << stud[i].num << " " << stud[i].name << " " << stud[i].score << endl;
    }
    iofile.close();

    return 0;
}

#虚函数
#include <iostream>
using namespace std;

class base  //定义基类
{
    public:
        virtual void who()  //虚函数声明
        {
            cout<<"this is the class of base !"<<endl;
        }
};

class derive1: public base  //定义派生类derive1
{
    public:
        void who()  //重新定义虚函数
        {
            cout << "this is the class of derive1 !" << endl;
        }
};

class derive2: public base  //定义派生类derive2
{
    public:
        void who()  //重新定义虚函数
        {
            cout << "this is the class of derive2 !" << endl;
        }
};

int main()
{
    base obj, *ptr; //声明基类对象obj、指针ptr
    derive1 obj1;   //声明派生类1的对象obj1
    derive2 obj2;   //声明派生类2的对象obj2
    ptr= &obj;  //基类指针指向基类对象
    ptr -> who();   //调用基类成员函数
    ptr = &obj1;    //基类指针指向派生类1对象
    ptr -> who();   //调用派生类1成员函数
    ptr=&obj2;  //基类指针指向派生类2对象
    ptr -> who();   //调用派生类2成员函数
    return 0;
}

#捕获异常
#include <iostream>

using namespace std;

int Div(int x,int y);

int main()
{
    try
    {
        cout<<"5/2="<<Div(5,2)<<endl;
        cout<<"8/0="<<Div(8,0)<<endl;
        cout<<"7/1="<<Div(7,1)<<endl;   //由于8/0抛出异常，所以7/1并没有运行
    }
    catch(int)
    {
        cout<<"except of deviding zero"<< endl;;
    }
    cout << "that is ok" << endl;
    return 0;
}

int Div(int x,int y)
{
    if(y==0)
    {
        throw y;
    }
    return x/y;
}

#include <iostream>
#include <string>

using namespace std;

class String
{
    char *name;
    int length;
    public:
        String(char *str)
        {
            length=strlen(str);
            name=new char[length+1];
            strcpy(name,str);
        }
        void show()
        {
            cout<<name<<endl;
        }
};

class de_string:public String
{
int age;
public:
    de_string(char *str, int age):String(str)
    {
        de_string::age=age;
    }
    void show()
    {
        String::show();
        cout<<"the age is:"<<age<<endl;
    }
};

int main()
{
    String s1("tony"),*ptr1;
    de_string s2("jack",20),*ptr2;
    ptr1=&s1;
    ptr1->show();
    ptr1=&s2;   //将ptr1指向String类的派生类de_string的对象s2
    ptr1->show();   //调用s2对象所属的基类的成员函数show()
    ptr2=&s2;
    ptr2 -> show();
    return 0;
}