Handling
of Sequence Control
Mathematical
Operators and Precedence
B provides operators for addition, subtraction, multiplication, division,
and exponentiation. Binary and unary operators have the same precedence.
Using parenthesis can change operator precedence.
Logical Operators
B provides logical operators for not, and, and or. The precedence is (),
not, and, and or.
Relational Operators
The relational operators < (less than), <=
(less than or equal to), >
(greater than), and >=
(greater than or equal to) take integer rvalue operands. The result is 1
if the operands are in the given relation to one another, and O otherwise.
Labels and Goto Statement
The goto statement
is as follows:
goto rvalue
;
The
rvalue is expected to be of type label. Control is then passed to the
corresponding label. Transfers into and out of compound statements are
legal, but use of labels as dummy arguments to transfer between functions
or function invocations is almost certain to cause disaster.
Statements
Statements
define program execution. Each statement is executed in sequence. There
are, of course, statements to conditionally or unconditionally alter
normal sequencing.
Most statements end with a semicolon ;.
Compound Statement
A
sequence of statements in {} braces is syntactically a single statement. This mechanism is provided
so that where a single statement is expected, any number of statements can
be placed.
Conditional Statement
A conditional statement has the general form:
if ( rvalue ) statement1
else statement2
;
This
evaluates rvalue and executes statement1 if the rvalue is
non-zero, and statement2 if the rvalue is zero.
The "else" clause is optional; thus:
if
( rvalue
) statement
executes statement if the rvalue is nonzero, and skips it if the
rvalue
is zero.
Break Statement
The
break statement has the syntax:
break
;
It is used to break
out of a compound statement controlled by a while statement; other
compound statements are ignored by it.
Return Statement
The return statement is
used in a function to return control to the caller of the function. The
first form simply returns control.
return ;
The second form
returns an rvalue for the execution of the function.
return ( rvalue
) ;
The caller of the function need not use the returned rvalue.
A return statement is automatically generated before the closing }
of a function definition.