HP 3000 Manuals HP 3000 Manuals
The switch Statement
The switch statement executes one or more of a series of cases based on
the value of an expression. It offers multiway branching.
Syntax
switch (expression)
statement
Description
The expression after the word switch is the controlling expression. The
controlling expression must have integral type. The statement following
the controlling expression is typically a compound statement. The
compound statement is called the switch body.
The statements in the switch body may be labeled with case labels. The
case label is followed by an integral constant expression and a colon.
No two case constant expressions in the same switch statment may have the
same value.
When the switch statement executes, integral promotions are performed on
the controlling expression; the result is compared with the constant
expressions after the case labels in the switch body. If one of the
constant expressions matches the value of the controlling expression,
control passes to the statement following that case expression.
If no expression matches the value of the control expression and a
statement in the switch body is labeled with the default label, control
passes to that statement. Only one statement of the switch body may be
labeled the default. By convention, the default label is included last
after the case labels, although this is not required by the C programming
language.
If there is no default, control passes to the statement immediately
following the switch body and the switch effectively becomes a
no-operation statement.
The switch statement operates like a multiway else-if chain except the
values in the case statements must be constant expressions, and, most
importantly, once a statement is selected from within the switch body,
control is passed from statement to statement as in a normal C program.
Control may "fall" through to following case statements. Using a break
statement is the most common way to leave a switch body. If a break
statement is encountered, control passes to the statement immediately
following the switch body.
Example
The following example shows a switch statement that includes several case
labels. The program selects the case whose constant matches getchar.
switch (getchar ( ) )
{
case 'r':
case 'R':
moveright ( );
break;
case 'l':
case 'L':
moveleft ( );
break;
case 'b':
case 'B':
moveback ( );
break;
case 'a':
case 'A':
default:
moveahead ( );
break;
}