Open Watcom FORTRAN 77 Language Reference

Program Structure Control Statements
9.10 SELECT - END SELECT
SELECT [CASE] (e) [FROM] [: block-label]
CASE ( case-list )
statement (s)
CASE ( case-list )
statement (s)
.
.
.
CASE DEFAULT
statement(s)
END SELECT
where:
case-list
is a list of one or more cases separated by commas. A case is either
(a)
(b)
a single integer, logical or character constant expression or
an integer, logical or character constant expression followed by a colon
followed by another expression or the same type. This form of a case defines
a range of values consisting of all integers or characters greater than or equal
to the value of the expression preceding the colon and less than or equal to
the value of the expression following the colon.
The SELECT construct, an extension to FORTRAN 77, is similar in concept to the FORTRAN computed
GO TO statement. It allows one of a number of blocks of code (case blocks) to be selected for execution by
means of an integer expression in the SELECT statement.
The SELECT statement keywords, CASE and FROM, are optional. The SELECT statement may contain a
block label (see the CYCLE, EXIT or QUIT statements for more information).
Each block must be started with a CASE statement; however, the last block may begin with a CASE
DEFAULT statement. The CASE DEFAULT block is optional. In order to retain compatibility with earlier
versions of WATCOM FORTRAN 77 compilers, the OTHERWISE statement may be used in place of the
CASE DEFAULT statement. The last block is ended by the END SELECT statement. The number of case
blocks is optional, from one to many; however, it is recommended that the SELECT construct not be used
for fewer than 3 case blocks. The conditional execution of one or two blocks of code is handled more
efficiently by the IF-THEN-ELSE construct.
A particular case value or range of values must not be contained in more than one CASE-block. For
example, the following is illegal:
SELECT - END SELECT 201