C++ program to create, write and read from data file using class fstream

/*
 C++ program to create, write and read from data file using class fstream
*/

#include "iostream"
#include "fstream" // required 
using namespace std;

int main(){
 /* Block to write to file */
 fstream fileOb;
 fileOb.open("MyFile", ios::out | ios::in); 
 if(fileOb.is_open()){
  cout<<"\nSuccess .."<<endl;
  fileOb<<"First Line added to file. \n"; // operator << have been overloaded for putting contents into file
  fileOb<<"Second line added. \n"; 
  fileOb<<"Third line added. \n"; 
 
  //fileOb.close();  // close the file
 }else{
  cout<<"\nFile creation and opening failed .. "<<endl;
 }

C++ program to add user defined contents to file and to read the file later

/*
 C++ program to add user defined contents to file and to read the file later
*/

#include "iostream"
#include "fstream" // required 
using namespace std;

int main(){
 /* Block to write user-defined contents to file */
 int count, age;
 string name;
 ofstream outFile;
 outFile.open("MyFile", ios::out); // writing ios::out is optional as object used is outFile
 if(outFile.is_open()){
  cout<<"\nSuccess .."<<endl;
  cout<<"\nHow many entries do you wish to add to file: ";
  cin>>count;
  for(int i=0; i<count; i++){
   cout<<"\nEnter name: ";
   cin>>name;
   cout<<"\nEnter age: ";
   cin>>age;
   
   outFile<<name<<"\t"<<age<<endl;  // adding contents to file
  }
 

C++ program to create, write and read from data file

/*
 C++ program to create, write and read from data file
*/

#include "iostream"
#include "fstream" // required 
using namespace std;

int main(){
 /* Block to write to file */
 ofstream outFile;
 outFile.open("MyFile", ios::out); // writing ios::out is optional as object used is outFile
 if(outFile.is_open()){
  cout<<"\nSuccess .."<<endl;
  outFile<<"First Line added to file. \n"; // operator << have been overloaded for putting contents into file
  outFile<<"Second line even added. \n"; 
 
  outFile.close();  // close the file
 }else{
  cout<<"\nFile creation and opening failed .. "<<endl;
 }

Class templates having single level inheritance in C++

/*
 Class templates having single level inheritance 
*/
#include "iostream"
using namespace std;

template <class T>
class First{
 T x;
 public:
  void getFirst(T a){
   x = a;
  }
  void showFirst(){
   cout<<"\nx: "<<x<<endl;
  }
};

template <class T2>
class Second: public First<T2>{
 T2 y, z;
 public:
  Second(T2 m, T2 n){
   y = m;
   z = n;
  }
  void showAll(){
//   display();
   cout<<"\ny: "<<y<<"\tz: "<<z<<endl;
  }
};

Class template having function template definition outside class in C++

/*
 Class template having function template definition
 Note: If you write showData() definition outside class in normal way, means without template
 then age and name wont be accessible. thats the reason showData() is defined inside.
*/
#include "iostream"
using namespace std;

template <class T1, class T2>
class Person{
 T1 age;
 T2 name;
 public:
  void getData();
  void showData(){
   cout<<"\nage: "<<age<<"\tname: "<<name<<endl;
  }
};
template <class T1, class T2> void Person<T1,T2>:: getData(){
 cin>>age>>name;
}

Simple class template having simple function template in C++

/*
 Simple class template having simple function template
*/
#include "iostream"
using namespace std;

template <class T>
class Person{
 T age;
 public:
 void getData(T a){
  age = a;
 }
 T showData();
};

Class template having default and parameterized constructors in C++

/*
 Class template having default and parameterized constructors
*/

#include "iostream"
using namespace std;

template <typename T1, class T2>
class Person{
 T1 age;
 T2 name;
 public:
  Person(){
   age = 32; 
   name = "Pavan";
  }
  Person(T1 x, T2 y){
   age = x;
   name = y;
  }
 
  void display(){
   cout<<"\nAge: "<<age<<"\tname: "<<name<<endl;
  }
};

Class template in C++ to accept and display person details

/*
 Class template which have data members of different types
*/

#include "iostream"
using namespace std;

template <class T1, typename T2>
class Person{
 T1 age;
 T2 name;
 public:
  void getData(){
   cout<<"\nEnter age & name ";
   cin>>age>>name;
  }
 
  void showData(){
   cout<<"\nage: "<<age<<"\tname: "<<name<<endl;
  }
};

Function template with two generic types in C++

/*
 Function template with two generic types
*/

#include "iostream"
using namespace std;

template <class T1, class T2>
void display(T1 xx, T2 yy){
 cout<<endl<<xx<<" "<<yy;
}

Function template to swap two numbers in C++

/*
 Demonstrating function template
*/

#include "iostream"
using namespace std;

template <class T>
void swaparg(T &a, T &b){
 T temp;
 temp = a;
 a = b;
 b = temp;
}

Function template to check max numebr in C++

/*
 Function template demo to check max number in c++ 
*/
#include "iostream"
using namespace std;

template <typename T>
T getMax(T x, T y){
 return (x>y?x:y);
}

int main(){
 cout<<"Max No: "<< getMax <int> (4,5)<<endl;
 return 0;
}
/*
 OUTPUT
[pavan@localhost Template]$ g++ FunctionTemplate.cpp
[pavan@localhost Template]$ ./a.out 
Max No: 5
[pavan@localhost Template]$ 

*/

Smart pointer in C++

/*
 Smart pointer demonstration
 -- smart pointer as name suggest works smart. 
 -- In case of normal pointer, delete is expected to be called explicitley. 
 -- In case pf smart pointer, destruction happens automatically even though some exception occurs 
*/

#include "iostream"
using namespace std;

class Person{
 int age;
 char *name;

 public:
  Person():age(0),name(0){
  }

  Person(int age, char* name):age(age), name(name){

  }
  ~Person(){ }
 
  void display(){
   cout<<"\nAge: "<<age<<"\t"<<name<<endl;
  }
};

New and delete in C++

/*
 New Delete Demo in C++
*/
#include "iostream"
#include <new> // Some time you may have to include this file

using namespace std;

int main(){
 int *var = new int(10); //allocating single block of memory and initializing there only
 cout<<"\nVar: "<<*var;
 *var = 50;
 cout<<"\nVar: "<<*var;
 cout<<endl;

Pointer to obejct with dynamic memory allocation in C++

/*
 Pointer to object with dynamic memory allocation
*/
#include "iostream"
using namespace std;

class Box{
 public: 
  Box(){
   cout<<"\nConstructor called..";
  }
  ~Box(){
   cout<<"\nDestructor called.."<<endl;
  }
};

Array of pointers to charecter in C++

/*
 Array of poniters to character
*/

#include "iostream"
using namespace std;
const int MAX=3;

int main(){
 char *name[MAX] = {
  "Pavan",
  "Jaiswal",
  "Pune" };
 cout<<"\n Printing character array elements \n";
 for(int i=0; i<MAX; i++){
  cout<<" "<<name[i]; // *name[i] prints first character of each string, say P J P
 }
 cout<<endl;
 return 0;
}

Array of pointers in C++

/*
 Array of pointers in C++
*/
#include "iostream"
using namespace std;
const int MAX=3;

int main(){
 int var[MAX] = {10,20,30};
 int *ptr[MAX];
 
 cout<<"\nPrinting Array elements \n";
 for(int i=0; i<MAX; i++)
  cout<<" "<<var[i];
 cout<<endl;

Function pointer used to do bubble sort in C++

/*
 Function Pointer used for bubble sort
*/

#include "iostream"
using namespace std;

int compare(int i, int j){
 if(i>j) return 1;
 else return -1;

}

Basic demo of function pointer for callback purpose in C++

/*
    Basic demo of function pointer for callback purpose
*/

#include "iostream"
using namespace std;

void meaningOfLife(){
    cout<<"\nHi"<<endl;
}

void printANumber(int num, void (*ptr)()){
    cout<<"\nnum: "<<num;
    (*ptr)(); // simply ptr();

}

Function pointer in C++

/*
 Demonstrating function pointer that takes two int args and return back int value
*/

#include "iostream"
using namespace std;

void printHello(){

 cout<<endl<<"Hello All"<<endl;
}

Add and display data to array using pointer notation

/*
 Insert and display data entered using pointer notation
*/

#include "iostream"
using namespace std;

int main(){
 int arr[5];
 
 cout<<"\nEnter 5 elements \n";
 for(int i=0; i<5; i++){
  cin>>*(arr+i);
 }

 cout<<"\n\nPrinting Array elements";
 for(int i=0; i<5; i++){
  cout<<"\n"<<*(arr+i);
 }