42 lines
1.2 KiB
C++
42 lines
1.2 KiB
C++
//Eg12-12.cpp
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#include <iostream>
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#include <cstring>
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#include <fstream>
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using namespace std;
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class Employee{
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private:
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int number ,age;
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char name[20];
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double sal;
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public:
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Employee(){}
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Employee(int num,char* Name,int Age, double Salary){
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number=num;
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strcpy(name,Name);
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age=Age;
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sal=Salary;
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}
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void display(){
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cout<<number<<"\t"<<name<<"\t"<<age<<"\t"<<sal<<endl;
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}
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};
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int main(){
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ofstream out("D:/Employee.dat",ios::out); //定义随机输出文件
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Employee e1(1,"张三",23,2320);
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Employee e2(2,"李四",32,3210);
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Employee e3(3,"王五",34,2220);
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Employee e4(4,"刘六",27,1220);
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out.write((char*)&e1,sizeof(e1)); //按e1,e2,e3,e4顺序写入文件
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out.write((char*)&e2,sizeof(e2));
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out.write((char*)&e3,sizeof(e3));
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out.write((char*)&e4,sizeof(e4));
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//下面的代码将e3（即王五）的年龄改为40岁
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Employee e5(3,"王五",40,2220);
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out.seekp(2*sizeof(e1)); //指针定位到第3（起始为0）个数据块，这里写错了应该是2*sizeof（e1）
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out.write((char*)&e5,sizeof(e5)); //将e5写到第3个数据块位置，覆盖e3
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out.close(); //关闭文件
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system("pause");
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}
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