Lecture 7Lecture 7

Introduction to Introduction to ProgrammingProgramming

while loopwhile loop

while (condition)while (condition)

{{

statements;statements;::

}}

statements;statements;

While loop executes zeroWhile loop executes zero

or more times. What if weor more times. What if we

want the loop to executewant the loop to execute

at least one time?at least one time?

do-whiledo-while

Do while loop execute Do while loop execute onon

or more timesor more times

Syntax of do-while Syntax of do-while looploop

dodo{{

statements ;statements ;

}}while ( condition ) ; while ( condition ) ;

Example-Guessing Example-Guessing gamegame

char c ;char c ; int tryNum = 1 ;int tryNum = 1 ; dodo {{

cout << "Please enter your guess by pressing a character key from cout << "Please enter your guess by pressing a character key from a to z “ ;a to z “ ; cin >> c ;cin >> c ; if ( c == 'z‘ )if ( c == 'z‘ )

{{ cout << "Congratulations! you guessed the right answer“ ;cout << "Congratulations! you guessed the right answer“ ; tryNum = 6 ;tryNum = 6 ;

}} elseelse

tryNum = tryNum + 1 ;tryNum = tryNum + 1 ; } while ( tryNum <= 5 ) ;} while ( tryNum <= 5 ) ;

Flow chart for do-while Flow chart for do-while looploop

Do-while

condition

Process

Exit

true

false

Relational Relational OperatorsOperators

char c ;char c ; int tryNum , maxTries ;int tryNum , maxTries ; tryNum = 1 ;tryNum = 1 ; maxTries = 5 ;maxTries = 5 ; cout << "Guess the alphabet between a to z “ ;cout << "Guess the alphabet between a to z “ ; cin >> c ;cin >> c ; while ( ( tryNum <= maxTries ) && ( c! = ‘z‘ ) )while ( ( tryNum <= maxTries ) && ( c! = ‘z‘ ) ) {{ cout << "Guess the alphabet cout << "Guess the alphabet

between a to z “ ;between a to z “ ; cin >> c ;cin >> c ; tryNum = tryNum + 1 ;tryNum = tryNum + 1 ; }}

for Loopfor Loop

For loopFor loop

forfor ( ( initialization condition initialization condition ; ; termination condition termination condition ; ; increment conditionincrement condition ) ) { {

statement ( s ) ;statement ( s ) ;}}

ExampleExampleint counter ;int counter ;

for( counter = 0 ; counter < 10 ; counter = counter + 1 )for( counter = 0 ; counter < 10 ; counter = counter + 1 )

cout << counter;cout << counter;

OutputOutput

01234567890123456789

Table for 2Table for 22 x 1 = 22 x 1 = 2

2 x 2 = 42 x 2 = 4

2 x 3 = 62 x 3 = 6

::

::

2 x 10 = 202 x 10 = 20

Example - Calculate Table Example - Calculate Table for 2for 2

#include <iostream.h>#include <iostream.h>

main ( )main ( )

{{

int counter ;int counter ;

for ( counter = 1 ; counter <= 10 ; counter = counter + 1 )for ( counter = 1 ; counter <= 10 ; counter = counter + 1 )

{{

cout << "2 x " << counter << " = " << 2* counter << "\n“ ;cout << "2 x " << counter << " = " << 2* counter << "\n“ ;

}}

}}

OutputOutput2 x1 = 22 x1 = 2

2 x 2 = 42 x 2 = 4

2 x 3 = 62 x 3 = 6

::

::

2 x 10 = 202 x 10 = 20

Flow chart for the ‘Table’ Flow chart for the ‘Table’ example example

counter=1

While

Print 2*counter

counter <=10?

Stop

Start

No Exit

Counter = counter + 1

yes

Example: Calculate Table- Example: Calculate Table- EnhancedEnhanced

#include <iostream.h>#include <iostream.h>main ( )main ( ){{ int number ;int number ; int maxMultiplier ;int maxMultiplier ; int counter ;int counter ; maxMultiplier = 10 ;maxMultiplier = 10 ; cout << " Please enter the number for which you wish to construct the table “ cout << " Please enter the number for which you wish to construct the table “

;; cin >> number ;cin >> number ; for ( counter = 1 ; counter <= maxMultiplier ; counter = counter + 1 )for ( counter = 1 ; counter <= maxMultiplier ; counter = counter + 1 ) {{ cout << number <<" x " << counter<< " = " << number * counter cout << number <<" x " << counter<< " = " << number * counter

<< "\n“ ;<< "\n“ ; }}}}

Always think re-useAlways think re-use Don’t use explicit Don’t use explicit

constantsconstants

Increment Increment operatoroperator

++++

counter ++ ; counter ++ ;

same as same as counter = counter + 1;counter = counter + 1;

Decrement Decrement operatoroperator

----

counter -- ;counter -- ;

same assame as counter = counter - 1counter = counter - 1

+=+= counter += 3 ; counter += 3 ;

same assame as counter = counter + 3 ;counter = counter + 3 ;

-=-= counter -= 5 ; counter -= 5 ;

same assame as counter = counter – 5 ;counter = counter – 5 ;

*=*=x*=2x*=2

x = x * 2x = x * 2

/=/=

x /= 2x /= 2

x = x / 2 x = x / 2

Compound Assignment Compound Assignment OperatorsOperators

operatoroperator==

%=%= x %= 2 ; x %= 2 ;

same as same as x = x % 2 ;x = x % 2 ;

CommentsComments Write comment at the top Write comment at the top

program to show what it doesprogram to show what it does Write comments that mean Write comments that mean

some thingsome thing

In today’s lectureIn today’s lecture Do - whileDo - while

– Executes the code at least onesExecutes the code at least ones For loopFor loop

– Executes at least zero timesExecutes at least zero times Short hand operatorsShort hand operators

– IncrementingIncrementing– DecrementingDecrementing

Compound assignment operatorCompound assignment operator