Programming in C

86 Chapter 6 Making Decisions

break;

case '-':

printf ("%.2f\n", value1 - value2);

break;

case '*':

printf ("%.2f\n", value1 * value2);

break;

case '/':

if ( value2 == 0 )

printf ("Division by zero.\n");

else

printf ("%.2f\n", value1 / value2);

break;

default:

printf ("Unknown operator.\n");

break;

}

return 0;

}

Program 6.9 Output

Type in your expression.

178.99 - 326.8

-147.81

After the expression has been read in, the value of operatoris successively compared

against the values as specified by each case.When a match is found, the statements con-

tained inside the case are executed.The breakstatement then sends execution out of the

switchstatement, where execution of the program is complete. If none of the cases

match the value of operator,the defaultcase, which displays Unknown operator.is

executed.

The breakstatement in the defaultcase is actually unnecessary in the preceding

program because no statements follow this case inside the switch.Nevertheless, it is a

good programming habit to remember to include the breakat the end of every case.

When writing a switchstatement, bear in mind that no two case values can be the

same. However, you can associate more than one case value with a particular set of

program statements.This is done simply by listing the multiple case values (with the

keyword casebefore the value and the colon after the value in each case) before the

common statements that are to be executed. As an example, in the following switch

statement, the printfstatement, which multiples value1by value2, is executed if

operatoris equal to an asterisk or to the lowercase letter x.

Program 6.9 Continued