Rockwell Automation 2098-IPD-xxx Ultra5000 C Programming using the Motion Library - Manual (Page 38)

Publication 2098-PM001E-EN-P — July 2002
1-26 Programming Motion Control in C
Switch
The switch statement performs a multiple path decision. It tests
whether an expression matches one of several constant integer values,
and branches accordingly. If no expression value matches, control
passes through each case until the default statement is encountered,
or no action takes place when the default option is absent.
switch (expression)
{
case expression1 : statement1;
case expression2 : statement2;
default : statement3;
}
Of course this assumes that each case is unique.
When control passes to a specific case, all subsequent cases in the
switch command are performed until the end of the switch, or a break
statement, is encountered, whichever occurs first.
switch (expression)
{
case expression1 : statement1;
break; /* if 1 runs, break
forces exit */
case expression2 : statement2;
break; /* if 2 runs, break
forces exit */
default: statement3;
break; /* break exits upon
default */
}
The break statement also forces an immediate exit from while, for,
and do loops.
While, For and Do-While Loops
The while statement creates a loop that repeats until the test
expression is false (zero).
while (expression)
statement; /* if expression is
non-zero, loop until
zero */
The for statement contains three expressions to control a loop. The
initialization (expression1) is performed once, before any of the loop
expressions are evaluated. If the test (expression2) is true (nonzero),