1.
C – switch structure
Technical Training
Titus

2.
if statement
• if...else statement provides support to control
program flow.
• if statement make decisions based on
conditions.
• It selects an action, if some condition is met.
2

3.
if limitations
• compare 2 numbers
– Greater than
– Less than
– Equal to
• Choice
1. Football
2. Hockey
3. Cricket
4. Volleyball
5. Basketball
3

4.
switch statement
• It selects an action, if some condition is met
• To make a decision from available choices
Eg.,-
– select a laptop from available models
– select a menu from available menu list etc.
4

5.
switch case
• switch...case statement gives ability to make
decisions from fixed available choices.
• not making decision based on conditions.
• using switch we can write a more clean and
optimal code, that take decisions from
available choices
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6.
flow
chart
6

7.
why switch case?
• with the if-else statement, the complexity of
the program increases whenever the number
of alternative path increases.
• using multiple if-else constructs in the
program might makes it difficult to read and
comprehend.
7

8.
syntax
switch(expression){
case 1:
/* Statement/s */
break;
case 2:
/* Statement/s */
break;
case n:
/* Statement/s */
break;
default:
/* Statement/s */
}
8

9.
if
for
number
of
choices
int num=3;
if(num==1)
printf("One");
if(num==2)
printf("Two");
if(num==3)
printf("Three");
if(num==4)
printf("Four");
if(num==5)
printf("Five");
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10.
if to switch
int num=1;
switch(num){
case 1: printf("One"); break;
case 2: printf("Two"); break;
case 3: printf("Three"); break;
case 4: printf("Four"); break;
case 5: printf("Five"); break;
}
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11.
int num=3;
if(num==1)
printf("One");
if(num==2)
printf("Two");
if(num==3)
printf("Three");
if(num==4)
printf("Four");
if(num==5)
printf("Five");
int num=1;
switch(num){
case 1: printf("One");
break;
case 2: printf("Two");
break;
case 3: printf("Three");
break;
case 4: printf("Four");
break;
case 5: printf("Five");
break;
}
11

12.
default in switch
int num=7;
switch(num){
case 1: printf("One"); break;
case 2: printf("Two"); break;
case 3: printf("Three"); break;
case 4: printf("Four"); break;
case 5: printf("Five"); break;
default: printf("not a valid choice");
}
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13.
rules:
• An expression must always execute to a result
• Case labels must be constants and unique
• Case labels must end with a colon ( : )
• A break keyword may be present in each case
• There can be only one default label
• We can nest multiple switch statements
• cases can be arranged in any order
– it is recommended to put them in ascending order
– It increases program readability
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14.
• The break statement is optional
– It transfers program flow outside of switch...case
• The default case is optional
– It works like an else block
• If no cases are matched then the control is
transferred to default block
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15.
odd or even – using switch
int number=8;
switch(number%2) { //this will give either 0 or 1
case 0:
printf("%d is an EVEN number.n“ ,number);
break;
case 1:
printf("%d is an ODD number.n“ ,number);
break;
}
15

16.
• Given the week day in number, convert that
into the day of the week
16

17.
int wDay=4;
switch(wDay) {
case 0:
printf("Sunday"); break;
case 1:
printf("Monday"); break;
case 2:
printf("Tuesday"); break;
case 3:
printf("Wednesday"); break;
case 4:
printf("Thursday"); break;
case 5:
printf("Friday"); break;
case 6:
printf("Saturday"); break;
default:
printf("Invalid weekday number.");
}
17

18.
• Find out whether the given character is a
vowel or not
18

19.
char ch='e';
switch(ch){
case 'a':
printf("Vowel"); break;
case 'e':
printf("Vowel"); break;
case 'i':
printf("Vowel"); break;
case 'o':
printf("Vowel"); break;
case 'u':
printf("Vowel"); break;
default:
printf("Consonant");
}
19

20.
fall through effect - used
• Side effects used to our advantage
20

21.
char ch='e';
switch(ch){
case 'a':
printf("Vowel"); break;
case 'e':
printf("Vowel"); break;
case 'i':
printf("Vowel"); break;
case 'o':
printf("Vowel"); break;
case 'u':
printf("Vowel"); break;
default:
printf("Consonant");
}
char ch='e';
switch(ch){
case 'a':
case 'e':
case 'i':
case 'o':
case 'u':
printf("Vowel"); break;
default:
printf("Consonant");
}
21

22.
• Write a program which will accept only 5 as a
valid input
22

23.
fall through effect
int i=5;
switch(i){
case 1:
case 2:
case 3:
case 4:
printf("wrong choice");
break;
case 5:
printf("right choice");
}
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24.
program to try
• Given the number of a month, find out how
many days are there in that month
24

25.
int month=6;
switch(month){
case 4:
case 6:
case 9:
case 11:
days=30;
break;
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
days=31;
break;
case 2:
days=28;
break;
default:
days=0;
break;
}
25

26.
guess the output
int x = 2;
switch (x){
case 1: printf("Choice is 1n");
case 2: printf("Choice is 2n");
case 3: printf("Choice is 3n");
case 4: printf("Choice is 4n");
break;
default: printf("Choice other than 1, 2, 3 and 4n");
break;
}
printf("After Switch");
26

27.
Output:
Choice is 2
Choice is 3
Choice is 4
After Switch
27

28.
default - anywhere
switch (x){
default: printf("Choice other than 1 and 2");
break;
case 1: printf("Choice is 1");
break;
case 2: printf("Choice is 2");
break;
}
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29.
case from an array index
switch (x)
{
case arr[0]: printf("Choice 1n");
case arr[1]: printf("Choice 2n");
case arr[2]: printf("Choice 3n");
}
29

30.
nested switch
int a = 100;
int b = 200;
switch(a) {
case 100:
printf("This is part of outer switchn", a );
switch(b) {
case 200:
printf("This is part of inner switchn", a );
}
}
printf("Exact value of a is : %dn", a );
printf("Exact value of b is : %dn", b );
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31.
limitations of switch...case
• switch...case work only with integer, character
and enumeration constant.
• case label must follow a constant. It does not
work with variables and expressions.
• programs written using switch...case can be
transformed to if...else...if. But not all
if...else...if programs can be converted to
switch...case.
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32.
points to ponder
• switch is a decision making construct in 'C'
• switch is used in a program where multiple decisions are
involved
• switch must contain an executable test-expression.
• each case may include a break keyword
• case label must be constants and unique
• default is optional
• multiple switch statements can be nested within one another.
• any number of statements are allowed in a case
• Statement(s) before the first case statement will not be
executed
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33.
conclusion
• Use if...else...if statement when -
– There are conditions instead of list of choices.
– There are few number of conditions.
• Use switch...case when -
– There is a list of choices, from which you need to
take decision.
– Choices are in the form of integer, character or
enumeration constant.
33

34.
• End 1
34

35.
Extras
35

36.
read weekday number and print weekday name
int main(){
int wDay;
printf("Enter weekday number (0-6): ");
scanf("%d",&wDay);
switch(wDay) {
case 0:
printf("Sunday");
break;
case 1:
printf("Monday");
break;
case 2:
printf("Tuesday");
break;
case 3:
printf("Wednesday");
break;
case 4:
printf("Thursday");
break;
case 5:
printf("Friday");
break;
case 6:
printf("Saturday");
break;
default:
printf("Invalid weekday number.");
}
printf("n");
return 0;
}
36

37.
• /*
• * To change this license header, choose License Headers in Project Properties.
• * To change this template file, choose Tools | Templates
• * and open the template in the editor.
• */
• /**
• *
• * @author Titus
• */
• public class SwitchCase2 {
• public static void main(String args[]) {
• // char grade = args[0].charAt(0);
• char grade = 'C';
• switch(grade) {
• case 'A' :
• System.out.println("Excellent!");
• break;
• case 'B' :
• case 'C' :
• System.out.println("Well done");
• break;
• case 'D' :
• System.out.println("You passed");
• case 'F' :
• System.out.println("Better try again");
• break;
• default :
• System.out.println("Invalid grade");
• }
• System.out.println("Your grade is " + grade);
• }
• }
• /*
• * To change this license header, choose License Headers in Project Properties.
• * To change this template file, choose Tools | Templates
• * and open the template in the editor.
• */
• /**
• *
• * @author Titus
• */
• public class SwitchCase2 {
• public static void main(String args[]) {
• // char grade = args[0].charAt(0);
• char grade = 'C';
• switch(grade) {
• case 'A' :
• System.out.println("Excellent!");
• break;
• case 'B' :
• case 'C' :
• System.out.println("Well done");
• break;
• case 'D' :
• System.out.println("You passed");
• case 'F' :
• System.out.println("Better try again");
• break;
• default :
• System.out.println("Invalid grade");
• }
• System.out.println("Your grade is " + grade);
• }
• }
37

38.
find number of days in a month using
switch case
#include <stdio.h>
int main()
{
int month;
int days;
printf("Enter month: ");
scanf("%d",&month);
switch(month)
{
case 4:
case 6:
case 9:
case 11:
days=30;
break;
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
days=31;
break;
case 2:
days=28;
break;
default:
days=0;
break;
}
if(days)
printf("Number of days in %d month is: %dn",month,days);
else
printf("You have entered an invalid month!!!n");
return 0;
}
#include <stdio.h>
int main()
{
int month;
int days;
printf("Enter month: ");
scanf("%d",&month);
switch(month)
{
case 4:
case 6:
case 9:
case 11:
days=30;
break;
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
days=31;
break;
case 2:
days=28;
break;
default:
days=0;
break;
}
if(days)
printf("Number of days in %d month is: %dn",month,days);
else
printf("You have entered an invalid month!!!n");
return 0;
}
38

39.
Print gender (Male/Female) - given M/F using
switch
• #include <stdio.h>
• int main()
• {
• char gender;
• printf("Enter gender (M/m or F/f): ");
• scanf("%c",&gender);
• switch(gender)
• {
• case 'M':
• case 'm':
• printf("Male.");
• break;
• case 'F':
• case 'f':
• printf("Female.");
• break;
• default:
• printf("Unspecified Gender.");
• }
• printf("n");
• return 0;
• }
• #include <stdio.h>
• int main()
• {
• char gender;
• printf("Enter gender (M/m or F/f): ");
• scanf("%c",&gender);
• switch(gender)
• {
• case 'M':
• case 'm':
• printf("Male.");
• break;
• case 'F':
• case 'f':
• printf("Female.");
• break;
• default:
• printf("Unspecified Gender.");
• }
• printf("n");
• return 0;
• }
39