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