#include<iostream.h>
class myclass{
  //private to myclass
  int a;
public:
  void set_a(int num);
  int get_a();
};

void myclass::set_a(int num)
{
  a=num;
}

int myclass::get_a()
{
  return a;
}
main()
{
  myclass ob1, ob2;
  ob1.set_a(10);
  ob2.set_a(99);

  cout<<ob1.get_a()<<"\n";
  cout<<ob2.get_a()<<"\n";
  return 0;
}

//This fragment contains an error.
#include <iostream.h>
 
main()
{
  myclass ob1,ob2;
  ob1.a=10;//ERROR! Cannot access private member
  ob2.a=99;//by non-member functions.

  cout << ob1.get_a()<<"\n";
  cout << ob2.get_a()<<"\n";
  
  return 0;
}

#include <iostream.h>

class myclass{
public:
  //now a is public
  int a;
  // and there is no need for set_a() or get_a()
};

main()
{
  myclass ob1, ob2;

  //here, a is accessed directly
  ob1.a=10;
  ob2.a=99;

  cout<<ob1.a << "\n";
  cout<<ob2.a << "\n";
return 0;
}

In this example, since a is declared as a public member of myclass, it is directly accesible from main. Notice How the dot operator is used to access a. In general, whether you are calling a member function or accessing a member variable, the objects name followed by the dot operator followed by the member's name is required to fully specify which object's member you are referring to.

#include <iostream.h>
#define SIZE 10
// Declare a stack class for characters
class stack{
  char stck[SIZE];//holds the stack
  int tos; //index of top-of-stack
  
public:
  void init(); //initialize stack
  void push(char ch); //push character on stack
  char pop(); //pop character from stack
};

// Initialize the stack
void stack::init()
{
  tos=0;
}

//Push a character
void stack::push(char ch)
{
  if(tos==SIZE){
    cout <<"Stack is full";
    return;
  }
  stck[tos]=ch;
  tos++;
}

//Pop a character.

char stack::pop()
{
  if(tos==0){
    cout <<"Stack is empty";
    return 0; //return null on empty stack
  }
  tos--;
  return stck[tos];
}
main()
{
  stack s1, s2; // Create two stacks.
  int i;
  // Initialize the stacks.
  
  s1.init();
  s2.init();

  s1.push('a');
  s2.push('x');
  s1.push('b');
  s2.push('y');
  s1.push('c');
  s2.push('z');

  for(i=0;i<3;i++) cout << "Pop s1:" << s1.pop() << "\n";
  for(i=0;i<3;i++) cout << "Pop s2:" << s2.pop() << "\n";
   
  return 0;
}

This Program displays the following output:
Pop s1: c
Pop s1: b
Pop s1: a
Pop s2: z
Pop s2: y
Pop s2: x

Chapter 1 More Examples





This program shows inline code encapsulation

#include <iostream.h>
#include <string.h>
 
class employee{
public:
  char name[64];
  long employee_id;
  float salary;
void show_employee(void)
    {
      cout << "Name: "<< name << endl;
      cout << "Id: "<< employee_id << endl;
      cout << "Salary: "<< salary << endl << endl;
    };
};
 
main (void)
{
  employee worker, boss;
 
  strcpy(worker.name, "John Doe");
  worker.employee_id = 7;
  worker.salary = 25000;
 
  strcpy(boss.name, "James Doe");
  boss.employee_id = 1;
  boss.salary = 55000;
 
  worker.show_employee();
  boss.show_employee();
 
return (0);
}


This program shows the concept of global resolution.

#include <iostream.h>
#include <string.h>
 
class dogs{
public:
  char breed[64];
  int avg_ht;
  int avg_wt;
  void show_breed(void);
};
 
void dogs::show_breed(void)
    {
      cout << "Breed: "<< breed << endl;
      cout << "Average Height: "<< avg_ht << endl;
      cout << "Average Weight: "<< avg_wt << endl << endl;
    }
 
main (void)
{
  dogs happy, matt;
 
  strcpy(happy.breed, "Dalmatian");
  happy.avg_ht = 58;
  happy.avg_wt = 24;
 
  strcpy(matt.breed, "Sheepdog");
  matt.avg_ht = 22;
  matt.avg_wt = 15;
 
  happy.show_breed();
  matt.show_breed();
 
return (0);
}

This program shows the concept of Function Overloading.

#include <iostream.h>
 
// overload abs() in three ways
int abs(int n);
long abs(long n);
double abs(double n);
 
 
main()
{
  cout <<"Absolute vaue of -10 :" << abs(-10) << endl;
  cout <<"Absolute vaue of -10L :" << abs(-10L) << endl;
  cout <<"Absolute vaue of -10.01 :" << abs(-10.01) << endl;
  return 0;
}
 
 
// abs() for ints
int abs(int n)
{
  cout << "Integer abs()" << endl;
  return n<0 ? -n : n;
}
 
 
// abs() for longs
long abs(long n)
{
  cout << "Long abs()" << endl;
  return n<0 ? -n : n;
}
 
 
// abs() for doubles
double abs(double n)
{
  cout << "Double abs()" << endl;
  return n<0 ? -n : n;
}



     


      Lecture 1: Notes