Introduction to Programming Lecture 38

Today’s Lecture User Define Manipulator Static key word

User Define Manipulators

Example int i = 10 ; cout << setwidth ( 7 ) << i <<endl ;

Parameter Less Manipulators

cout << manipulator << otherdata ;

ostream & manipulatorName ( ostream & os ) ;

Definition ostream & manipulatorName ( ostream & os ) { return os << userDefinedManipulator ; }

User Defined Manipulators A Short Example // Tab ostream & tab ( ostream & output ) { return output << '\t' ; } // bell ostream & bell ( ostream & output ) return output << '\a' ; // Takes the cursr to next line ostream & endLine ( ostream & output ) return output << '\n' << flush ; void main ( ) cout << "Virtual " << tab << "University" << bell << endLine ; // Use of Mainpulator

Static

Static Are variables which exist for a certain amount of time which is longer than an ordinary automatic variable.

Global

Example int i ; void myfunction ( void ) { for ( i = 0 ; i < 10 ; i ++ ) cout << i << endl ; }

Automatic Variable

State

static int i ;

static int i = 0 ; //Initialization ......... i = 0 ; //Ordinary Assignment Statement

Example void f ( void ) { static int i = 0 ; i ++ ; cout << “Inside function f value of i : ” << i << endl ; } main ( ) int j ; for ( j = 0 ; j < 10 ; j ++ ) ; f ( ) ;

Example class Truck { char a ; public : Truck ( char c ) a = c ; cout << "Inside constructor for object " << a << endl ; } ~ Truck ( ) cout << "Inside destructor for object " << a << endl ; } ;

Example Truck a ( 'A' ) ; main ( ) { Truck b ( 'B' ) ; f ( ) ; g ( ) ; cout << “Function g has been called " << endl ; }

Example void f ( ) { Truck c ( 'C' ) ; } void g ( ) static Truck g ( 'G' ) ;

Example Output Inside constructor for object A Inside constructor for object B Inside constructor for object C Inside destructor for object C Inside constructor for object G function g has been called Inside destructor for object B Inside destructor for object G Inside destructor for object A

Static Data Member Inside A Class

File Scope

Example class Truck { public : int wheels ; int seats ; } ; main ( ) Truck A ; A.seats ; }

Scope Resolution Operator ::

Truck :: nameOfStaticDatamember = values ;

Example class SavingsAccount { } ; private : char name [ 30 ] ; float accountNumber ; float currentBalance ; static float profitRate ; // ... public : SavingsAccount ( ) ; //... } ;

SavingsAccount :: profitRate = 3.0 ;

SavingsAccount A ; A.profitRate ; // bad usage

A.profitRate = 4.0 ; // bad usage

SavingsAccount :: profitRate ;

Example class Student { public : static int howMany ; Student ( ) { howMany ++ ; } ~ Student( ) { howMany -- ; } void displayHowMany ( ) cout << "Number of students are " << howMany ; } } ; int Student :: howMany = 0 ;

Dynamic

What we covered today Parameter Less Manipulation Static Data