Switch Case Statements in C and C++

1. Switch – Case Statements
By: Er. Aman Kumar

2. Switch-Case Statements
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3. • Switch case statement allows us to make
decisions from multiple choices.
• Integer expression must yield an integer value
like 1, 2, 3, etc. The keyword case is followed
by an integer or a character constant.
• Each constant in each case must be different
from all the others. The “do this” lines in the
above form of switch represent any valid C
statement.
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5. • break always used with the switch statement
to terminate the switch statement or to
prevent the entry in other case.
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8. The Tips and Traps
• It is not compulsory to put cases in ascending
order as we did above. We can place them in
any order we want.
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9. You are also allowed to use char
values in case and switch as
shown in the following program
(Program to find whether character
entered is vowel or not)
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11. Modified
Form
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12. If a statement doesn’t belong to any case the compiler
won’t report an error. However, the statement would
never get executed. For example, in the following
program the printf( ) never goes to work.
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13. • If there is no default in switch, then error will not be
there. If no case is matching, statements after switch
will execute.
• Relational Expression like i>5 are not allowed in any
case. Even float values not allowed in any case
• We can check the value of any expression in a switch.
Thus the following switch statements are legal.
switch ( i - j * k )
switch ( 3 + 9 % 4 * i )
switch ( a < 5 || b > 7 )
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14. • Expressions can also be used in cases provided they
are constant expressions. Thus case 13 + 7 is correct,
however, case a + b is incorrect.
• switch may occur within another, but in practice it is
rarely done. Such statements would be called nested
switch statements.
• The switch statement is very useful while writing
menu driven programs
• Even if there are multiple statements to be executed
in each case there is no need to enclose them
within a pair of braces (unlike if, and else).
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15. switch Versus if-else Ladder
Disadvantages of switch over if-else
• A float expression cannot be tested using a
switch
• Cases can never have variable expressions
(for example it is wrong to say case a +3 : )
• Multiple cases cannot use same expressions.
Thus the following switch is illegal:
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16. Advantages of switch over if-else
• compiler generates a jump table for a switch
during compilation. As a result, during
execution it simply refers the jump table to
decide which case should be executed, rather
than actually checking which case is satisfied.
• As against this, if-else are slower because they
are evaluated at execution time.
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