The switch Statement
This is another form of the multi way decision. It is well structured, but can only be used in certain cases where;
- Only one variable is tested, all branches must depend on the value of that variable. The variable must be an integral type. (int, long, short or char).
- Each possible value of the variable can control a single branch. A final, catch all, default branch may optionally be used to trap all unspecified cases.
Example given below will clarify things. This is a function which converts an integer into a vague description. It is useful where we are only concerned in measuring a quantity when it is quite small.
estimate(number)
int number;
/* Estimate a number as none, one, two, several, many */
{ switch(number) {
case 0 :
printf("None\n");
break;
case 1 :
printf("One\n");
break;
case 2 :
printf("Two\n");
break;
case 3 :
case 4 :
case 5 :
printf("Several\n");
break;
default :
printf("Many\n");
break;
}
}
Each interesting case is listed with a corresponding action. The break statement prevents any further statements from being executed by leaving the switch. Since case 3 and case 4 have no following break, they continue on allowing the same action for several values of number.
Both if and switch constructs allow the programmer to make a selection from a number of possible actions. Let us see an example:
#include <stdio.h>
int main()
{
int num;
for (num = 3 ; num < 13 ; num = num + 1)
{
switch (num)
{
case 3 :
printf("The value is three\n");
break;
case 4 :
printf("The value is four\n");
break;
case 5 :
case 6 :
case 7 :
case 8 :
printf("The value is between 5 and 8\n");
break;
case 11 :
printf("The value is eleven\n");
break;
default :
printf("It is one of the undefined values\n");
break;
} /* end of switch */
} /* end of for loop */
return 0;
}
The output of the program will be
The value is three
The value is four
The value is between 5 and 8
The value is between 5 and 8
The value is between 5 and 8
The value is between 5 and 8
It is one of the undefined values
It is one of the undefined values
The value is eleven
It is one of the undefined values |
|
