Jump statements cause an unconditional jump to another statement
elsewhere in the code. They are used primarily to interrupt
switch statements and loops.
The jump statements are the goto statement, the
continue statement, the break statement,
and the return statement, which are discussed in the
following sections.
The goto statement unconditionally transfers program
control to a labeled statement, where the label identifier is
in the scope of the function containing the goto
statement. The labeled statement is the next statement executed.
The goto statement has the following syntax:
goto identifier;
Care must be taken when branching into a block by using the
goto statement, because storage is allocated for
automatic variables declared within a block when the block is
activated. When a goto statement branches into a block,
automatic variables declared in the block are not initialized.
The continue statement passes control to the end of
the immediately enclosing while , do , or
for statement. The continue statement has
the following syntax:
continue;
The continue statement is equivalent to a
goto statement within an iteration statement that
passes control to the end of the loop body. For example, the
following two loops are equivalent:
while(1) while(1)
{ {
. .
. .
. .
goto label_1; continue;
. .
. .
. .
label_1:
; ;
} }
The continue statement can be used only in loops. A
continue inside a switch statement that is
inside a loop causes continued execution of the enclosing loop after
exiting from the body of the switch statement.
The break statement terminates execution of the
immediately enclosing while , do ,
for , or switch statement. Control passes
to the statement following the loop body (or the compound statement
of a switch statement). The break
statement has the following syntax:
break;
See Example 7-1 which uses a
break statement within a switch statement.
The return statement terminates execution of a
function and returns control to the calling function, with or
without a return value. A function may contain any number of
return statements. The return statement
has the following syntax:
return expression(opt);
If present, the expression is evaluated and its value is returned to the calling function. If necessary, its value is converted to the declared type of the containing function's return value.
A return statement with an expression cannot appear
in a function whose return type is void . For more
information about the void data type and function
return types, see Sections 3.5 and 3.4.1.
If there is no expression and the function is not defined as
void , the return value is undefined. For example,
the following main function returns an unpredictable
value to the operating system:
main ( )
{
return;
}
Reaching the closing brace that terminates a function is equivalent
to executing a return statement without an expression.