C++

1.Complete File I/O program in C++ using Objects in MinGW compiler

#include<iostream>
#include<fstream>
#include<iomanip>

using namespace std;


class student
{
protected:
char name[20];
char address[50];
int roll;
float marks;

public:
       void getdata()
        {
        cout<<"Enter the name:";cin>>name;
        cout<<"Enter the address:";cin>>address;
        cout<<"Enter the roll no:";cin>>roll;
        cout<<"Enter the marks:";cin>>marks;
        }

        void putdata()
        {

        cout<<setw(10)<<name<<setw(15)
        <<address<<setw(10)<<roll
        <<setprecision(2)<<setw(10)
        <<marks<<endl;
        }
     
};


int main()
{
student std;
fstream inout("RECORD.txt",ios::ate|ios::binary|ios::in|ios::out);
cout<<"What do you like to do?"<<"\n";
cout<<"Enter 1 to write into file:\n";
cout<<"Enter 2 to display the content of file:"<<"\n";
cout<<"Enter 3 to update record in file:"<<"\n";
cout<<"Enter 4 to modify record of student:"<<"\n";
cout<<"Enter 5 to count number of objects in file:"<<"\n";
int m;
cin>>m;

switch(m)
{
case 1:
       {
     
       inout.seekg(0,ios::beg);
       int z;
       cout<<"Enter the number of students";cin>>z;
       for(int k=1;k<=z;k++)
          {
          std.getdata();
          inout.write(reinterpret_cast<const char *>(&std),sizeof(std));
          }
          inout.clear();
          break;

    }



//Displays current contents
case 2:
       {
     
        inout.seekg(0,ios::beg);
        cout<<"current contents of file"<<"\n";
        cout<<setw(10)<<"Name"<<setw(15)
        <<"Address"<<setw(10)<<"Roll"
        <<setprecision(2)<<setw(10)
        <<"Marks"<<endl;
       while(inout.read(reinterpret_cast<char *>(&std),sizeof(std)))
         {
         std.putdata();
         }
       inout.clear();
       break;
       }

//update student record
case 3:
       {
       cout<<"\n Add a student \n";
       std.getdata();
       char ch;
       cin.get(ch);
       inout.write(reinterpret_cast<const char *> (&std),sizeof(std));
       cout<<"Record Added";
       break;
       }
case 4:
       {
       cout<<"Enter the object number to be modified"<<endl;
       int object,location;
       cin>>object;
       location=(object-1)*sizeof(std);
       inout.seekg(location);
       cout<<"Enter the new data"<<endl;
       std.getdata();
       inout.write(reinterpret_cast<const char *> (&std),sizeof(std));
       cout<<"Record modified"<<endl;
       break;
       }
case 5:
      {
   
      int last=inout.tellg();
      int n=last/sizeof(std);
      cout<<"Total number of objects:"<<n<<"\n";
      cout<<"Total size of file:"<<last<<"bytes";
      break;
      }
default:
       {
       cout<<"\nWrong choice";
       }
}

inout.close(); //closing the file
return 0;
}


2.Exception Handling 1:
#include<iostream>
using namespace std;

int main()
{
int i,j,a,x;
cout<<"Enter three numbers a,i and j"<<endl;
cin>>a>>i>>j;
x=i-j;
try
{
 if(x==0)
  throw(x);
 else
 cout<<"The result of a/x is:"<<a/x;
}
catch(int k)
 {
   cout<<"Exception caught:X=0"<<endl<<
    "Division by zero is undefined"<<endl;
 }

}

3.Exception Handling 2:
#include<iostream>

using namespace std;

void divide(int x,int y,int z)
{
cout<<"We are inside function:"<<endl;
int r=x-y;
if(r!=0)
cout<<"result of z/r"<<z/r<<endl;
else
throw(x-y);
}



int main()
{
try
{
cout<<"We are inside try block"<<endl;
divide(20,10,30);
divide(10,10,30);

}
catch(int i)
{
cout<<"Exception caught"<<"X="<<i<<endl;
}
return 0;

}



4.Class and Object Concept:
#include<iostream>

using namespace std;

class student
{
private:
int roll;char name[25];long int tel_no;float score;
public:
void getdata()
{
cout<<"Enter the roll number,name,telephone number and score of student"<<endl;
cin>>roll>>name>>tel_no>>score;
}
void showdata()
{
cout<<"Name:"<<name<<endl<<"Roll:"<<roll<<endl<<"Telephone number"<<tel_no<<endl
    <<"Score:"<<score<<endl;
}
void rank();
};

void student::rank()
{
if(score>80) cout<<"Distinction";
else if(score>50 && score<80) cout<<"First Division";
else if(score>40 && score<50) cout<<"Second Division";
else if(score>32 && score<40) cout<<"Third Division";
else cout<<"Failed";
}

int main()
{
student s1,s2;
s1.getdata();
s1.showdata();
s1.rank();
s2.getdata();
s2.showdata();
s2.rank();
return 0;

}



5.Adding two complex numbers using Class and Object Concept:
#include<iostream>
using namespace std;

class complex
{

float re,im;

public:

complex(int a,int b)
{
re=a;im=b;
}

complex()//Constructor
{
float x,y;
cout<<"Enter complex number of form a+ib";
cin>>x>>y;
re=x;im=y;
}

void sum(complex cc1,complex cc2)//Evaluates sum
{
re=cc1.re+cc2.re;
im=cc1.im+cc2.im;
}

void showdata()
{
cout<<"the sum is"<<endl<<"Re="<<re<<endl<<"Im="<<im<<endl;
}

};


int main()
{
complex c1,c2;
complex c3(0,0);
c3.sum(c1,c2);
c3.showdata();
return 0;

}

6.Function overloading:In calculating Area of different geometries
#include<iostream>

using namespace std;

const float p=3.14;

float area(float r)
{
return (p*r*r);
}

int area(int a,int b)
{
return(a*b);
}

int main()
{
float r;
int a,b;
cout<<"Enter the radius of the circle"<<endl;
cin>>r;
cout<<"Enter the length and breadth of a rectangle"<<endl;
cin>>a>>b;
cout<<"The area of circle is "<<area(r)<<endl<<"and that of rectangle is "<<area(a,b);
return 0;
}

7.Adding three complex numbers using binary operator overloading
#include<iostream>

using namespace std;

class complex
{
float re;
float im;
public:
void getdata()
{
cout<<"Enter a complex number a+ib"<<endl;
cin>>re>>im;
}
void setdata()
{
cout<<"Enter another complex number c+id"<<endl;
cin>>re>>im;
}
void Enterdata()
{
cout<<"Enter another complex number e+if"<<endl;
cin>>re>>im;
}

complex operator +(complex c2)
{
complex c;
c.re=re+c2.re;
c.im=im+c2.im;
return c;
}
void showdata()
{
cout<<"The sum is"<<re<<"+"<<"i"<<im<<endl;
}
};

int main()
{
complex c1,c2,c3,c4;
c1.getdata();
c2.setdata();
c3.Enterdata();
c4=c1+c2+c3;
c4.showdata();
return 100;

}


8.Concept of Constructor and Destructor
#include<iostream>
using namespace std;

class test
{
public:
test()
{
cout<<"The control is inside the constructor"<<"\n";
cout<<"The object is in itialized here"<<"\n";
}
~test()
{
cout<<"The control is inside the destructor"<<"\n";
cout<<"The object goes out of scope"<<"\n";
cout<<"Clean up process is done"<<"\n";
}
};

int main()
{
test a;//constuctor called
cout<<"Main function terminating........."<<"\n";
cout<<"Object a goes out of scope"<<"\n";
return 0;
}

9.Concept of Reference in C++
#include<iostream>

using namespace std;

float &assign(float&,float&);

int main()
{
cout<<"Enter any two numbers"<<endl;
float a,b;
cin>>a>>b;
cout<<"Before calling"<<endl;
cout<<"a="<<a<<endl<<"b="<<b<<endl;
float smaller=assign(a,b);
cout<<"After calling function"<<endl;
cout<<"smaller="<<smaller;
return 0;
}

float &assign(float&x,float&y)
{
if(x<y)
return x;
else
return y;
}