Lecture 4 Introduction to Programming. if ( grade ==‘A’ ) cout
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Transcript of Lecture 4 Introduction to Programming. if ( grade ==‘A’ ) cout
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
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?
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 ) ;
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
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“ ;
}}
}}
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“ ; }}}}
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
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
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
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
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 ” ;
}}
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 (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 ;
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 …
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