Open Watcom FORTRAN 77 Language Reference

Language Reference
READ statement to be executed when an end of file condition is encountered during the READ and to be
by-passed immediately following a READ statement. It is not valid to use this control statement with
direct-access or memory-to-memory reads. Clearly, it is not valid to use this statement when END= is
specified in the READ statement.
Example:
READ(7, *) I, X
AT END DO
PRINT *, ’END-OF-FILE ENCOUNTERED’
EOFSW = .TRUE.
END AT END
If the READ statement is executed without encountering end of file, control passes to the statement
following the END AT END statement. If an end of file condition occurs during the read, the string,
END-OF-FILE ENCOUNTERED is printed, logical variable EOFSW is assigned the value .TRUE. and
control passes to the statement following the END AT END statement.
Example:
READ(7, *) X
AT END, EOFSW = .TRUE.
If an end of file is not encountered by the READ statement, control passes to the statement following the AT
END statement. If an end-of-file condition occurs, variable EOFSW is set to .TRUE. and control then
passes to the statement following the AT END statement. Note that the use of the second form of the AT
END statement requires the use of a comma (,) between the AT END word and the executable statement.
This is necessary to distinguish the case where the executable statement is an assignment statement. The
executable statement may be any statement that is also allowed as the operand of a logical IF statement.
9.17 Notes on Structured Programming Statements
In addition to the definitions and examples of these constructs, the following points should be noted:
(i)
Any of the new control statements with their blocks may be used within the block of any
other statement. For example, a WHILE-block may contain another WHILE or an
IF-THEN-ELSE block. Blocks may be nested in this manner to any level within storage
limitations. An important exception to this rule is the REMOTE-block A REMOTE-block
may contain other types of blocks (nested to any level); however, another REMOTE-block
may not be defined within it. Furthermore, REMOTE-blocks may not be defined within
another control structure. The following example is illegal.
Example:
* Illegal definition of a REMOTE-block.
IF( I .EQ. 3 )then
REMOTE BLOCK A
.
.
.
END BLOCK
END IF
(ii)
When nesting blocks, the inner blocks must always be completed with the appropriate
block-terminating END statement before the outer blocks are terminated. Similarly, when
nesting blocks with DO-loops, a DO-loop started within a block must be completed before
212 Notes on Structured Programming Statements