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46 lines
1.2 KiB
C++
46 lines
1.2 KiB
C++
// Eg12-12.cpp
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#include <cstring>
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#include <fstream>
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#include <iostream>
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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(
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2 *
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sizeof(
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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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}
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