classthatwrites.cpp (#733)

It is a C++ program which gives a demo for using IO classes in C++.

Author: VARADSP

IO_operations_C/classthatwrites.cpp

@@ -0,0 +1,87 @@
+//person  objects do disk IO
+#include<iostream>
+#include<fstream>
+using namespace std;
+class person
+{
+private:
+    char name[40];
+    int age;
+public:
+    void getData()
+    {
+        cout << "\n Enter last name : " ; cin >> name;
+        cout << "\n Enter age : " ; cin >> age;
+    }
+    void showData()
+    {
+        cout << "\n Name : " << name;
+        cout << "\n Age : " << age;
+    }
+    void diskIn(int);
+    void diskOut();
+    static int diskCount();
+};
+void person::diskIn(int pn)
+{
+    ifstream infile;
+    infile.open("Person.dat",ios::binary);
+    infile.seekg(pn*sizeof(person));
+    infile.read((char *)this,sizeof(*this));
+}
+void person::diskOut()
+{
+    ofstream outfile;
+    outfile.open("Person.dat",ios::app | ios::binary);
+    outfile.write((char *)this,sizeof(*this));
+}
+int person::diskCount()
+{
+ifstream infile;
+infile.open("Person.dat",ios::binary);
+infile.seekg(0,ios::end);
+return (int)infile.tellg()/sizeof(person);
+}
+int main()
+{
+    person p;
+    char ch;
+    do
+    {
+        cout << "Enter data for person :: ";
+        p.getData();
+        p.diskOut();
+        cout << "\nDo another (y/n)?";
+        cin >> ch;
+    }while(ch=='y');
+    int n = person::diskCount();
+    cout << "\n There are " << n << " persons in file\n";
+    for(int j=0;j<n;j++)
+    {
+        cout << "\nPerson " << j;
+        p.diskIn(j);
+        p.showData();
+    }
+    cout << endl;
+    return 0;
+}
+/*
+Input:
+Enter data for person :: 
+ Enter last name : varad
+ Enter age : 22
+Do another (y/n)?y
+Enter data for person :: 
+ Enter last name : akshay
+ Enter age : 19
+Do another (y/n)?n
+
+Output:
+ There are 2 persons in file
+Person 0
+ Name : varad
+ Age : 22
+Person 1
+ Name : akshay
+ Age : 19
+*/