cs201- introduction to programming- lecture 08

Introduction to Introduction to ProgrammingProgramming

Lecture No. 8Lecture No. 8

LoopsLoops– WhileWhile– Do whileDo while– ForFor

OperatorsOperators– Increment / DecrementIncrement / Decrement– Compound Assignment OperatorsCompound Assignment Operators

In the last In the last lecturelecture

int sum;int sum;int students ;int students ;int average ;int average ;sum = 0 ;sum = 0 ;students = 0 ;students = 0 ;dodo{{

cin >> grade ;cin >> grade ;sum += grade ;sum += grade ;students ++ ;students ++ ;

}}while (grade >= 0) ; while (grade >= 0) ; average = sum / students ;average = sum / students ;cout << average ; cout << average ;

Example: Program to Example: Program to calculate the average marks calculate the average marks

of class of class

A Flaw in the code

Multi-way decision Multi-way decision

if ( grade ==‘A’ )if ( grade ==‘A’ )cout << “ Excellent ” ;cout << “ Excellent ” ;

if ( grade ==‘B’ )if ( grade ==‘B’ )cout << “ Very Good ” ;cout << “ Very Good ” ;

if ( grade ==‘C’ )if ( grade ==‘C’ )cout << “ Good ” ;cout << “ Good ” ;

if ( grade ==‘D’ )if ( grade ==‘D’ )cout << “ Poor ” ;cout << “ Poor ” ;

if ( grade ==‘F’ )if ( grade ==‘F’ )cout << “ Fail ” ;cout << “ Fail ” ;

if Statementsif Statements

if ( grade ==‘A’ )if ( grade ==‘A’ )cout << “ Excellent ” ;cout << “ Excellent ” ;

else else if ( grade ==‘B’ )if ( grade ==‘B’ )

cout << “ Very cout << “ Very Good ” ;Good ” ;

elseelseif ( grade ==‘C’ )if ( grade ==‘C’ )

cout << “ Good ” ;cout << “ Good ” ;elseelse

if ( grade ==‘D’ )if ( grade ==‘D’ )cout << “ Poor ” ;cout << “ Poor ” ;

if elseif else

if ( grade == ‘A’ )if ( grade == ‘A’ )

cout << “ Excellent ” ;cout << “ Excellent ” ;

else if ( grade == ‘B’ )else if ( grade == ‘B’ )

……

else if …else if …

……

else …else …

if elseif else

switch statementswitch statement

switch statementsswitch statements

switch ( variable name )switch ( variable name ){{

case ‘a’ :case ‘a’ :statements;statements;

case ‘b’ :case ‘b’ :statements;statements;

case ‘c’ :case ‘c’ : statements; statements;

……}}

switch ( grade)switch ( grade){{

case ‘A’ :case ‘A’ :cout << “ Excellent ” ;cout << “ Excellent ” ;

case ‘B’ :case ‘B’ :cout << “ Very Good ” cout << “ Very Good ”

;;case ‘C’ :case ‘C’ :

…………

}}

switch statements switch statements

case ‘A’ :case ‘A’ :cout << “ Excellent ” ;cout << “ Excellent ” ;…………

switch statements

ExampleExample

switch ( grade)switch ( grade){{

case ‘A’ :case ‘A’ :cout << “ Excellent ” ;cout << “ Excellent ” ;

case ‘B’ :case ‘B’ :cout << “ Very Good ” ;cout << “ Very Good ” ;

case ‘C’ :case ‘C’ :cout << “Good ” ; cout << “Good ” ;

case ‘D’ :case ‘D’ :cout << “ Poor ” ;cout << “ Poor ” ;

case ‘F’ :case ‘F’ :cout << “ Fail ” ;cout << “ Fail ” ;

}}

break;break;

ExampleExampleswitch ( grade )switch ( grade ){{

case ‘A’ :case ‘A’ :cout << “ Excellent ” ;cout << “ Excellent ” ;break ;break ;

case ‘B’ :case ‘B’ :cout << “ Very Good ” ;cout << “ Very Good ” ; break ; break ;

case ‘C’ :case ‘C’ :cout << “Good ” ; cout << “Good ” ; break ;break ;

case ‘D’ :case ‘D’ :cout << “ Poor ” ;cout << “ Poor ” ; break ; break ;

case ‘F’ :case ‘F’ :cout << “ Fail ” ;cout << “ Fail ” ; break ; break ;

}}

default :default :

cout << “ Please Enter Grade cout << “ Please Enter Grade from ‘A’ to ‘D’ or ‘F’ “ ;from ‘A’ to ‘D’ or ‘F’ “ ;

default :default :

switch (grade)

Display “Excellent”

case ‘B’ :

case ‘A’ :

Display “Very Good”

Default :

“……..”

Flow Chart of switch Flow Chart of switch statementstatement

…

if ( amount > 2335.09 ) if ( amount > 2335.09 ) statements ;statements ;

Whole NumberWhole Number shortshort intint longlong

case ‘A’ :case ‘A’ :case ‘ 300 ‘ :case ‘ 300 ‘ :case ‘ f ‘ :case ‘ f ‘ :

if (c == ‘z’ )if (c == ‘z’ )

{{

cout << “ Great ! You have made the correct guess “ ;cout << “ Great ! You have made the correct guess “ ;break ;break ;

}}

break ;break ;

continue ;continue ;

continuecontinuewhile trynum <= 5 ;while trynum <= 5 ;

{{

……..

……..

continue ;continue ;

}}

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

{{

…………..

continue ;continue ;

}}

continue in ‘for’ continue in ‘for’ looploop

Sequential StatementsSequential Statements DecisionsDecisions

– if , if else , switchif , if else , switch LoopsLoops

– while , do while , forwhile , do while , for

What have we done till now …What have we done till now …

gotogotoUnconditional Branch of ExecutionUnconditional Branch of Execution

SequencesSequences DecisionsDecisions LoopsLoops

Structured Structured ProgrammingProgramming

Minimize the use of breakMinimize the use of break Minimize the use of Minimize the use of

continuecontinue Never use gotoNever use goto

Guide lines for Guide lines for structured structured

programmingprogramming

Modular Modular Single entry - single exitSingle entry - single exit

Rule 1 : Use the simplest flowchartRule 1 : Use the simplest flowchart

Rule 2 : Any rectangle can be replaced Rule 2 : Any rectangle can be replaced by by two rectangles. two rectangles.

Rule 3 : Any rectangle can be replaced Rule 3 : Any rectangle can be replaced with with

structured flowcharting structured flowcharting constructs. constructs.

Rule 4 : It says, rule 2 and rule 3 can beRule 4 : It says, rule 2 and rule 3 can be

repeated as many times as repeated as many times as neededneeded

Rules for Structured Rules for Structured FlowchartFlowchart

Data StructuresData Structures– ArraysArrays

Character StringsCharacter Strings PointersPointers

Next MilestonesNext Milestones