The data member of a class is declared within the body of
the class. However, the member functions can be defined in one of the two
places.
- Inside the class definition
- Outside the class definition
No matter whether the function is defines inside or outside
the class definition, the function performs the same operation. But the syntax
of the member function definition is different if declared inside or outside. The
program code written inside the body of member function is the same whether it
is declared inside or outside.
- Inside the class definition:
The general syntax of the function
definition inside class definition will be as:
class classname
{
//……………..
public:
return_type
member_function(args…)
{
//function
body
}
};
Following example illustrates the
definition of function inside class definition:
Source Code:
//definition inside the class
#include<iostream>
using namespace std;
class student
{
private:
int
roll;
char
name[20];
char
phone[10];
public:
void
getdata()
{
cout<<"\nEnter
Roll Number: ";
cin>>roll;
cout<<"Enter
Name: ";
cin>>name;
cout<<"Enter
Phone Number: ";
cin>>phone;
}
void
showdata()
{
cout<<"Name:
"<<name<<endl;
cout<<"Roll
Number: "<<roll<<endl;
cout<<"Phone
Number: "<<phone<<endl;
}
}; //end of class
int main()
{
student
s1, s2;
s1.getdata();
s2.getdata();
cout<<"First
Student"<<endl;
s1.showdata();
cout<<"Second
Student"<<endl;
s2.showdata();
return
0;
}
Sample Run:
Enter Roll Number: 1
Enter Name: John
Enter Phone Number: 1234567890
Enter Roll Number: 2
Enter Name: Marrie
Enter Phone Number: 9876543210
First Student
Name: John
Roll Number: 1
Phone Number: 1234567890
Second Student
Name: Marrie
Roll Number: 2
Phone Number: 9876543210
2. Outside the class definition:
The general syntax of the function
definition outside class definition will be as:
class classname
{
//……………..
public:
return_type
member_function(args…);
//…………….
};
Return_type class_name::member_function(args…)
{
//function
body
}
The declaration can be done in private or
public section.
We have presented the same example
presented above where member functions are defined outside the class
specification.
Source Code:
//definition outside the class
#include<iostream>
using namespace std;
class student
{
private:
int
roll;
char
name[20];
char
phone[10];
public:
void
getdata(); //function declaration
void
showdata();
}; //end of class
void student::getdata() //function definition
{
cout<<"\nEnter
Roll Number: ";
cin>>roll;
cout<<"Enter
Name: ";
cin>>name;
cout<<"Enter
Phone Number: ";
cin>>phone;
}
void student::showdata()
{
cout<<"Name:
"<<name<<endl;
cout<<"Roll
Number: "<<roll<<endl;
cout<<"Phone
Number: "<<phone<<endl;
}
int main()
{
student
s1, s2;
s1.getdata();
s2.getdata();
cout<<"First
Student"<<endl;
s1.showdata();
cout<<"Second
Student"<<endl;
s2.showdata();
return
0;
}
Sample Run:
Enter Roll Number: 1
Enter Name: John
Enter Phone Number: 1234567890
Enter Roll Number: 2
Enter Name: Marrie
Enter Phone Number: 9876543210
First Student
Name: John
Roll Number: 1
Phone Number: 1234567890
Second Student
Name: Marrie
Roll Number: 2
Phone Number: 9876543210
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