Post on 06-Feb-2016
description
Control Statement - Selection
if Statements
ifif
if - elseif - else
if – else - ifif – else - if
if Statement
Syntax:if (expression)if (expression)
statement;statement;or
if (expression) {if (expression) {statement1;statement1;statement2;statement2;
}}
Syntax:if (expression)if (expression)
statement;statement;or
if (expression) {if (expression) {statement1;statement1;statement2;statement2;
}}
Don’t forget the curly Don’t forget the curly brackets, if there are more brackets, if there are more
than ONE statementsthan ONE statements
Don’t forget the Don’t forget the brackets !!brackets !!
if Statement
Pseudo Code:if <condition is true> start
step 1
step 2
…
step k
end_if
Pseudo Code:if <condition is true> start
step 1
step 2
…
step k
end_if
if Statement:
if (<condition>) {
statement 1
statement 2
…statement k
}
if Statement:
if (<condition>) {
statement 1
statement 2
…statement k
}
if Statement
Example:int num1, num2, min;printf(“Key-in 2 numbers: “);scanf(“%d%d”, &num1, &num2);min = num1;if (num1 > num2)
min = num2;printf(“Smallest: %d\n”, min);
Example:int num1, num2, min;printf(“Key-in 2 numbers: “);scanf(“%d%d”, &num1, &num2);min = num1;if (num1 > num2)
min = num2;printf(“Smallest: %d\n”, min);
Key-in 2 numbers: _
num2 ?
num1 ?
min ?
Key-in 2 numbers: 20 15
_
20
15
2015
Key-in 2 numbers: 20 15
Smallest: 15
_
20 > 15?20 > 15?
if Statement
Example:void main() {
int mark;
printf(“Mark: “);
scanf(“%d”, &mark);
if (mark >= 50)
printf(“Pass\n”);
printf(“Your mark is %d”, mark);}
Example:void main() {
int mark;
printf(“Mark: “);
scanf(“%d”, &mark);
if (mark >= 50)
printf(“Pass\n”);
printf(“Your mark is %d”, mark);}
What will the output What will the output be if the mark is 65?be if the mark is 65?
if Statement
Example:void main() {
int mark;
printf(“Mark: “);
scanf(“%d”, &mark);
if (mark >= 50)
printf(“Pass\n”);printf(“Your mark is %d”, mark);
}
Example:void main() {
int mark;
printf(“Mark: “);
scanf(“%d”, &mark);
if (mark >= 50)
printf(“Pass\n”);printf(“Your mark is %d”, mark);
}
What will the output What will the output be if the mark is 35?be if the mark is 35?
if - else Statement
Syntax:if (expression)if (expression)
statement1;statement1;elseelse
statement2;statement2;or
if (expression) {if (expression) {statement1;statement1;statement2;statement2;
} else} elsestatement3;statement3;
Syntax:if (expression)if (expression)
statement1;statement1;elseelse
statement2;statement2;or
if (expression) {if (expression) {statement1;statement1;statement2;statement2;
} else} elsestatement3;statement3;
if - else Statement
orif (expression) {if (expression) {
statement1;statement1;statement2;statement2;
} else {} else {statement3;statement3;statement4;statement4;
}}
orif (expression) {if (expression) {
statement1;statement1;statement2;statement2;
} else {} else {statement3;statement3;statement4;statement4;
}}
if - else Statement
Example:if (num1 < num2)
min = num1;
else
min = num2;
printf(“Smallest: %d\n”, min);
Example:if (num1 < num2)
min = num1;
else
min = num2;
printf(“Smallest: %d\n”, min);
num2 15
num1 10
min ?
10 < 15?10 < 15?
_
10
Smallest: 10
_
if - else Statement
Example:if (num1 < num2)
min = num1;
else
min = num2;
printf(“Smallest: %d\n”, min);
Example:if (num1 < num2)
min = num1;
else
min = num2;
printf(“Smallest: %d\n”, min);
num2 15
num1 20
min ?
20 < 15?20 < 15?
_
15
Smallest: 15
_
if - else Statement
Example:if (num1 < num2) {
min = num1;max = num2;
}else {
min = num2;max = num1;
}printf(“Min = %d, Max = %d\n”, min, max);
Example:if (num1 < num2) {
min = num1;max = num2;
}else {
min = num2;max = num1;
}printf(“Min = %d, Max = %d\n”, min, max);
num2 125
num1 700
min ??
700 < 125?700 < 125?
_
max ??
Min = 125, Max = 700
_
125
700
if – else Statement
Example:void main() {
int mark;
printf(“Mark: “);scanf(“%d”, &mark);if (mark >= 50)
printf(“Pass\n”);else
printf(“Fail\n”);printf(“Your mark is %d”, mark);
}
Example:void main() {
int mark;
printf(“Mark: “);scanf(“%d”, &mark);if (mark >= 50)
printf(“Pass\n”);else
printf(“Fail\n”);printf(“Your mark is %d”, mark);
}
What will the output What will the output be if the mark is 21?be if the mark is 21?
What will the output What will the output be if the mark is 74?be if the mark is 74?
if – else Statement
Example:void main() {
int mark;
printf(“Mark: “);scanf(“%d”, &mark);if (mark >= 50)
printf(“Pass\n”);else
printf(“Fail\n”);printf(“Your mark is %d”, mark);
}
Example:void main() {
int mark;
printf(“Mark: “);scanf(“%d”, &mark);if (mark >= 50)
printf(“Pass\n”);else
printf(“Fail\n”);printf(“Your mark is %d”, mark);
}
What will the output What will the output be if the mark is 74?be if the mark is 74?
What will the output What will the output be if the mark is 14?be if the mark is 14?
if – else Statement
Example:void main() {
int mark;printf(“Mark: “);scanf(“%d”, &mark);if (mark >= 50)
printf(“Pass\n”);else {
printf(“Fail\n”);printf(“Your mark is %d”, mark);
}}
Example:void main() {
int mark;printf(“Mark: “);scanf(“%d”, &mark);if (mark >= 50)
printf(“Pass\n”);else {
printf(“Fail\n”);printf(“Your mark is %d”, mark);
}}
What will the output What will the output be if the mark is 14?be if the mark is 14?
What will the output What will the output be if the mark is 70?be if the mark is 70?
Take a break … (Learn styles)
Example:void main() {
int mark;printf(“Mark: “);scanf(“%d”, &mark);if (mark >= 50)
printf(“Pass\n”);
else printf(“Fail\n”);
printf(“Your mark is %d”, mark);}
Example:void main() {
int mark;printf(“Mark: “);scanf(“%d”, &mark);if (mark >= 50)
printf(“Pass\n”);
else printf(“Fail\n”);
printf(“Your mark is %d”, mark);}
Take a break … (Learn styles)
Example:void main() {
int mark;printf(“Mark: “);scanf(“%d”, &mark);if (mark >= 50)printf(“Pass\n”);
else printf(“Fail\n”);
printf(“Your mark is %d”, mark);}
Example:void main() {
int mark;printf(“Mark: “);scanf(“%d”, &mark);if (mark >= 50)printf(“Pass\n”);
else printf(“Fail\n”);
printf(“Your mark is %d”, mark);}
Difficult to read!!!Difficult to read!!!Don’t you think Don’t you think so??so??
Syntax:if (expression)if (expression)
statement;statement;
Syntax:if (expression)if (expression)
statement;statement;
if statementif statement
Let’s recap …
Syntax:if (expression)if (expression)
statement;statement;else else
statement;statement;
Syntax:if (expression)if (expression)
statement;statement;else else
statement;statement;
if-else statementif-else statement
Ok now, let’s look at Ok now, let’s look at if – else –ifif – else –if statement statement
if – else - if Statement
Syntax:if (expression)if (expression)
statement;statement;else if (expression)else if (expression)
statement;statement;
Syntax:if (expression)if (expression)
statement;statement;else if (expression)else if (expression)
statement;statement;
if-else-if statementif-else-if statementSyntax:
if (expression)if (expression)statement;statement;
else if (expression)else if (expression)statement;statement;
else if (expression)else if (expression)statement;statement;
elseelsestatement;statement;
Syntax:if (expression)if (expression)
statement;statement;else if (expression)else if (expression)
statement;statement;else if (expression)else if (expression)
statement;statement;elseelse
statement;statement;
if-else-if statementif-else-if statement
if – else - if Statement
Syntax:if (expression)if (expression)
statement;statement;else if (expression)else if (expression)
statement;statement;else if (expression)else if (expression)
statement;statement;else else (expression)(expression)
statement;statement;
Syntax:if (expression)if (expression)
statement;statement;else if (expression)else if (expression)
statement;statement;else if (expression)else if (expression)
statement;statement;else else (expression)(expression)
statement;statement;
if-else-if statementif-else-if statement
Be careful…common Be careful…common mistake made by mistake made by
students !!students !!
Let’s recap …
Example:if <condition_1 is true> start
step m…
end_ifif <condition_2 is true> start
step n…
end_ifelse start
step x…
end_else
Example:if <condition_1 is true> start
step m…
end_ifif <condition_2 is true> start
step n…
end_ifelse start
step x…
end_else
Multiple SelectionMultiple Selection
Assume condition 1 is Assume condition 1 is true, so …true, so …
step m, step …. will be step m, step …. will be executedexecuted
Let’s recap …
Example:if <condition_1 is true> start
step m…
end_ifif <condition_2 is true> start
step n…
end_ifelse start
step x…
end_else
Example:if <condition_1 is true> start
step m…
end_ifif <condition_2 is true> start
step n…
end_ifelse start
step x…
end_else
Multiple SelectionMultiple Selection
Assume condition 1 is Assume condition 1 is false, so …false, so …
• step m, step …. will be step m, step …. will be skipped, and skipped, and
• condition 2 will be testedcondition 2 will be tested
Let’s recap …
Example:if <condition_1 is true> start
step m…
end_ifif <condition_2 is true> start
step n…
end_ifelse start
step x…
end_else
Example:if <condition_1 is true> start
step m…
end_ifif <condition_2 is true> start
step n…
end_ifelse start
step x…
end_else
Multiple SelectionMultiple Selection
Assume condition 2 is Assume condition 2 is true, so …true, so …
step n, step …. will be step n, step …. will be executedexecuted
Let’s recap …
Example:if <condition_1 is true> start
step m…
end_ifif <condition_2 is true> start
step n…
end_ifelse start
step x…
end_else
Example:if <condition_1 is true> start
step m…
end_ifif <condition_2 is true> start
step n…
end_ifelse start
step x…
end_else
Multiple SelectionMultiple Selection
Assume condition 2 is also Assume condition 2 is also false, so …false, so …
• step n, step …. will be step n, step …. will be skipped, and skipped, and
• step x will be executedstep x will be executed
Multiple Selection in C
Example:#include <stdio.h>int main( ) {
char letter;
scanf(“%c”, &letter);if (letter >= ‘a’ && letter <= ‘z’ )
printf(“Lower case\n”);else if (letter >= ‘A’ && letter <= ‘Z’)
printf(“Upper case\n”);else if (letter >= ‘0’ && letter <= ‘9’)
printf(“Digit\n”);else
printf(“Special character\n”);}
Example:#include <stdio.h>int main( ) {
char letter;
scanf(“%c”, &letter);if (letter >= ‘a’ && letter <= ‘z’ )
printf(“Lower case\n”);else if (letter >= ‘A’ && letter <= ‘Z’)
printf(“Upper case\n”);else if (letter >= ‘0’ && letter <= ‘9’)
printf(“Digit\n”);else
printf(“Special character\n”);}
Is the letter a lower case? Is the letter a lower case?
Is the letter an upper case? Is the letter an upper case?
Is the letter a digit? Is the letter a digit?
Multiple Selection in C
Example:#include <stdio.h>int main( ) {
char letter;
scanf(“%c”, &letter);if (letter >= ‘a’ && letter <= ‘z’ )
printf(“Lower case\n”);else if (letter >= ‘A’ && letter <= ‘Z’)
printf(“Upper case\n”);else if (letter >= ‘0’ && letter <= ‘9’)
printf(“Digit\n”);else
printf(“Special character\n”);}
Example:#include <stdio.h>int main( ) {
char letter;
scanf(“%c”, &letter);if (letter >= ‘a’ && letter <= ‘z’ )
printf(“Lower case\n”);else if (letter >= ‘A’ && letter <= ‘Z’)
printf(“Upper case\n”);else if (letter >= ‘0’ && letter <= ‘9’)
printf(“Digit\n”);else
printf(“Special character\n”);}
(the letter is a lower case) (the letter is a lower case) truetrue
(the letter is a lower case) (the letter is a lower case) falsefalse(the letter is an upper case) (the letter is an upper case) truetrue(the letter is a lower case) (the letter is a lower case) falsefalse
(the letter is an upper case) (the letter is an upper case) falsefalse(the letter is a digit) (the letter is a digit) truetrue
(the letter is a lower case) (the letter is a lower case) falsefalse(the letter is an upper case) (the letter is an upper case) falsefalse
(the letter is a digit) (the letter is a digit) falsefalse
ExerciseDevelop a program for the following problem.
Given a mark, determine its grade based on the table below:
75 < mark < 100 grade = A65 < mark < 74 grade = B55 < mark < 64 grade = C40 < mark < 54 grade = D 0 < mark < 39 grade = F others error message
Pseudo CodeStartInput student’s markIf student’s mark is greater than or equal to 75
Print “Grade = A”else If student’s mark is greater than or equal to 65 and lower than 75
Print “Grade = B”else If student’s mark is greater than or equal to 55 and lower than 65
Print “Grade = C”else If student’s mark is greater than or equal to 40 and lower than 55
Print “Grade = D”else If student’s mark is greater than or equal to 0 and lower than 40
Print “Grade = F”else
Print “Input error”End
Answer1
int mark;printf(“Key-in the mark: “);scanf(“%d”,&mark);if ((mark >= 75) && (mark <= 100))
printf("Grade = A”);else if ((mark >= 65) && (mark <= 74))
printf(" Grade = B”); else if ((mark >= 55) && (mark <= 64))
printf(" Grade = C”);else if ((mark >= 40) && (mark <= 54))
printf(" Grade = D”);else if ((mark >= 0) && (mark <= 39))
printf(" Grade = E”);else
printf(“Input error\n”);
Answer2
int mark;char grade ;printf(“Key-in the mark : “);scanf(“%d”,&mark);if ((mark >= 75) && (mark <= 100))
grade =‘A’;else if ((mark >= 65) && (mark <= 74))
grade =‘B’; else if ((mark >= 55) && (mark <= 64))
grade =‘C’;else if ((mark >= 40) && (mark <= 54))
grade =‘D’;else if ((mark >= 0) && (mark <= 39))
grade =‘E’;else
printf(“Input error\n”);printf(“Your grade is %c”, grade );
Answer3
int mark;char grade;printf(“Key-in the mark: “);scanf(“%d”,&mark);if ((mark >= 75) && (mark <= 100))
grade=‘A’;else if ((mark >= 65) && (mark <= 74))
grade=‘B’; else if ((mark >= 55) && (mark <= 64))
grade=‘C’;else if ((mark >= 40) && (mark <= 54))
grade=‘D’;else if ((mark >= 0) && (mark <= 39))
grade=‘E’;if ((mark > 100) || (mark < 0))
printf(“Input error\n”);else
printf(“Your grade is %c”, grade);
Nested ifs
ifif statement that contains other ifif / if - elseif - else statements
Nested ifs
Example:if (age > 18) {
if (age > 55) price = 2.50; /* Price for senior citizens
*/else
price = 5.00; /* Price for adults */}else {
if (age < 1)price = 0.0; /* Price for infants */
elseprice = 1.50; /* for children &
teenagers*/}
Example:if (age > 18) {
if (age > 55) price = 2.50; /* Price for senior citizens
*/else
price = 5.00; /* Price for adults */}else {
if (age < 1)price = 0.0; /* Price for infants */
elseprice = 1.50; /* for children &
teenagers*/}
This price is valid for This price is valid for people: age > 55people: age > 55
This price is valid for This price is valid for people: 18 < age < 55people: 18 < age < 55
This price is valid for This price is valid for people: age < 1people: age < 1
This price is valid for This price is valid for people: 1 < age < 18people: 1 < age < 18
Nested ifs - Problem
Example:if (age > 18)
if (age > 55) price = 2.50; /* Price for senior citizens */
elseprice = 5.00; /* Price for adults */
Example:if (age > 18)
if (age > 55) price = 2.50; /* Price for senior citizens */
elseprice = 5.00; /* Price for adults */
Which Which ifif does this does this elseelse belong to? belong to?
Nested ifs - ProblemTry to understand the consequences….
if (age > 18) {
if (age > 55)
price = 2.50;
else
price = 5.00;
}
if (age > 18) {
if (age > 55)
price = 2.50;
else
price = 5.00;
}
if (age > 18) {
if (age > 55)
price = 2.50;
}
else
price = 5.00;
if (age > 18) {
if (age > 55)
price = 2.50;
}
else
price = 5.00;
Nested ifs - Problem
By default, elseelse will be attached to the nearest ifif
if (age > 18)
if (age > 55)
price = 2.50;
else
price = 5.00;
if (age > 18)
if (age > 55)
price = 2.50;
else
price = 5.00;
if (age > 18) {
if (age > 55)
price = 2.50;
else
price = 5.00;
}
if (age > 18) {
if (age > 55)
price = 2.50;
else
price = 5.00;
}
switch and break
Syntax:switch (expression) {switch (expression) {
case expression1:case expression1:statement1;statement1;break;break;
case expression2:case expression2:statement2;statement2;break;break;
……default:default:
expressionX;expressionX;break;break;
}}
Syntax:switch (expression) {switch (expression) {
case expression1:case expression1:statement1;statement1;break;break;
case expression2:case expression2:statement2;statement2;break;break;
……default:default:
expressionX;expressionX;break;break;
}}
Syntax:switchswitch (expression) { (expression) {
casecase expression1: expression1:statement1;statement1;break;break;
casecase expression2: expression2:statement2;statement2;break;break;
……defaultdefault::
expressionX;expressionX;break;break;
}}
Syntax:switchswitch (expression) { (expression) {
casecase expression1: expression1:statement1;statement1;break;break;
casecase expression2: expression2:statement2;statement2;break;break;
……defaultdefault::
expressionX;expressionX;break;break;
}}
Don’t forget the Don’t forget the brackets !!brackets !!
Don’t forget the Don’t forget the curly brackets !!curly brackets !!
Don’t forget the Don’t forget the colons !!colons !!
switchswitch and and breakbreak Important Rule !!
Syntax:switchswitch (expression) { (expression) {
casecase expression1: expression1:statement1;statement1;break;break;
casecase expression2: expression2:statement2;statement2;break;break;
……defaultdefault::
expressionX;expressionX;break;break;
}}
Syntax:switchswitch (expression) { (expression) {
casecase expression1: expression1:statement1;statement1;break;break;
casecase expression2: expression2:statement2;statement2;break;break;
……defaultdefault::
expressionX;expressionX;break;break;
}}
Must be Must be INTEGER or INTEGER or
CHAR !CHAR !
switch and break
Example: switch (month) {case 1:
printf(“January\n”);break;
case 2:printf(“February\n”);break;
case 3:printf(“March\n”);break;
default:printf(“Others\n”);break;
} printf(“End”);
Example: switch (month) {case 1:
printf(“January\n”);break;
case 2:printf(“February\n”);break;
case 3:printf(“March\n”);break;
default:printf(“Others\n”);break;
} printf(“End”);
Assume month = 1, Assume month = 1, so …so …
……this step will be this step will be executed. Later …executed. Later ………casecase is terminated is terminated here. Jump to …here. Jump to …
January
_
January
End _
switch and break
Example: switch (month) {case 1:
printf(“January\n”);break;
case 2:printf(“February\n”);break;
case 3:printf(“March\n”);break;
default:printf(“Others\n”);break;
} printf(“End”);
Example: switch (month) {case 1:
printf(“January\n”);break;
case 2:printf(“February\n”);break;
case 3:printf(“March\n”);break;
default:printf(“Others\n”);break;
} printf(“End”);
……this step will be this step will be executed. Later …executed. Later …
March
_
March
End _
Assume month = 3, Assume month = 3, so …so …
……casecase is terminated is terminated here. Jump to …here. Jump to …
switch and break
Example: switch (month) {case 1:
printf(“January\n”);break;
case 2:printf(“February\n”);break;
case 3:printf(“March\n”);break;
default:printf(“Others\n”);break;
}printf(“End”);
Example: switch (month) {case 1:
printf(“January\n”);break;
case 2:printf(“February\n”);break;
case 3:printf(“March\n”);break;
default:printf(“Others\n”);break;
}printf(“End”);
Now…what will Now…what will happen if this happen if this breakbreak is taken out from the is taken out from the
program?program?
Example: switch (month) {case 1:
printf(“January\n”);break;
case 2:printf(“February\n”);
case 3:printf(“March\n”);break;
default:printf(“Others\n”);break;
} printf(“End”);
Example: switch (month) {case 1:
printf(“January\n”);break;
case 2:printf(“February\n”);
case 3:printf(“March\n”);break;
default:printf(“Others\n”);break;
} printf(“End”);
No more !!No more !!
switch and break
Example: switch (month) {case 1:
printf(“January\n”);break;
case 2:printf(“February\n”);
case 3:printf(“March\n”);break;
default:printf(“Others\n”);break;
} printf(“End”);
Example: switch (month) {case 1:
printf(“January\n”);break;
case 2:printf(“February\n”);
case 3:printf(“March\n”);break;
default:printf(“Others\n”);break;
} printf(“End”);
……this step will be this step will be executed. Later …executed. Later …
February
_
February
March
_
Assume month = 2, Assume month = 2, so …so …
……casecase is terminated is terminated here. Jump to …here. Jump to …
February
March
End _
……execution continues. Thus, execution continues. Thus, this step is executed . So …this step is executed . So …
switch and break
Example: switch (month) {case 1:
printf(“January\n”);break;
case 2:printf(“February\n”);
case 3:printf(“March\n”);break;
default:printf(“Others\n”);break;
} printf(“End”);
Example: switch (month) {case 1:
printf(“January\n”);break;
case 2:printf(“February\n”);
case 3:printf(“March\n”);break;
default:printf(“Others\n”);break;
} printf(“End”);
Now…what will Now…what will happen if these happen if these
breakbreaks are taken out s are taken out from the program?from the program?
And … And … if month = 1 ?if month = 1 ?And … And … if month = 34 ?if month = 34 ?
switch and break
Example: char jantina;printf (“Masukkan Jantina Anda: (L/P)\n”);scanf (“%c”,&jantina);
switch (jantina) {case ‘P’:
printf(“\nJantina adalah PEREMPUAN\n”);
break;case ‘L’:
printf(“\nJantina adalah LELAKI”);break;
default:printf(“\nTIDAK DAPAT DIPASTIKAN!”);break;
}
Example: char jantina;printf (“Masukkan Jantina Anda: (L/P)\n”);scanf (“%c”,&jantina);
switch (jantina) {case ‘P’:
printf(“\nJantina adalah PEREMPUAN\n”);
break;case ‘L’:
printf(“\nJantina adalah LELAKI”);break;
default:printf(“\nTIDAK DAPAT DIPASTIKAN!”);break;
}
Masukkan Jantina Anda: (L/P)
L
Masukkan Jantina Anda: (L/P)
L
Jantina adalah LELAKI
jantina ?L
End of Lecture
Review Questions