The switch case is a programming
construct in C/C++ which allows us to match the result of an expression to
certain cases and then display the matching statement. Let us read in details
about switch case.
The switch() Statement in C/C++ :
C++ provides a multiple-branch
selection statement known as switch. This selection statement successively
tests the value of an expression against a list of integer or character
constants. When a match is found, the statements associated with that constant
are executed.
The general syntax of switch statement :
The exp is evaluated and its value
is matched against the values of the constants specified in the case statements. When a match is found, the statement sequence associated with that case starts
executing. The control goes on executing all the following sequences till it
encounters break or it reaches the end of switch.
If a case statement
does not include a break statement, then the control continues right on
the next case statements until a break is encountered or the end of
switch is reached. This situation (missing break in case statements) is
called fall through.
The default case is executed when no
match is found. The default statement is optional, and
if it is not present, the control simply comes out of the switch block if none
of the cases match.
Whenever a break
statement is encountered in a switch statement, program execution jumps out of
the switch block to the line immediately after switch.
The following flowchart
represents basic working of a switch statement.
Points to keep in mind while using switch case :
First, the expression provided
in the switch should result in character or integer type constant. Otherwise,
the switch statement becomes invalid and compiler shows error.
Example :
Valid
expressions – switch(1+3*6)
switch(1*2/9%3)
variables can
also be used but they should be storing some integer or character value – switch(a+b*c)
Second, two cases cannot have the
same constant, i.e. duplicate cases are not allowed.
Third, the default statement is
optional and is executed when none of the cases match the value of the expression.
Fourth, break is an important
keyword in switch case. It is optional but should be carefully used in order to
avoid fall through.
Fifth, Nesting of switch case is
allowed, i.e. there may be one or more switch cases inside the parent switch
block. But it is generally avoided as it makes the program complex and reduces readability.
Sixth, all case constants must
be either character type or integer type. Also, C++ allows constant variables (declared
using const) as case constants but C doesn’t. So, for switch statement in C,
all case constants must be literals and not associated with any variable. For
instance, the code
const int a=1;const
int b=2;
switch(1)
{
case a
: cout<< 1 ;break;
case b
: cout<< 2 ;break;
default : cout<< “more than 2”;
}
works fine with
C++ compiler but shows error in C.
Here is a
sample program to find greater of two numbers using switch case :
#include<iostream>
using namespace
std;
int main()
{
int a,b; cin>>a>>b;
switch ((int)(a>b))
{
case 0: cout<<b<< “ is greater ”;
break;
case 1 : cout<<a<< “is greater ”;
}
return 0;
}
Input : 60 68
Output : 68 is
greater
An interesting
exercise for you is to write the following programs using if-else and then
using switch.
1. Check if a
character is vowel or not. Take input from user.
2. Print the day
of the week depending on the number input by user. Assume the number to be
between 1 to 7 with 1 being Monday and 7 being Sunday.
Try making a
simple calculator using switch case.
I am not
including solutions so that you may practice it yourself. If you want to share
your code or ask any doubt you can comment on this post or you can mail me at coding.nkcoder@gmail.com.
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