Open Watcom FORTRAN 77 Language Reference

Language Reference
Example:
LOOP
READ *, X
AT END, EXIT
PRINT *, X
END LOOP
The above statements read and print values until an end of file occurs. At that point control is passed to the
EXIT statement, as specified by the AT END statement. The EXIT statement causes control to continue
with the statement after the END LOOP statement.
Example:
CHARACTER RECORD(80)
LOOP : RDREC
READ(5,100) RECORD
AT END, STOP
DO I = 1, 80
IF( RECORD(I) .LT. ’0’
+ .OR. RECORD(I) .GT. ’9’ )EXIT : RDREC
END DO
WRITE(6,101) RECORD
END LOOP
PRINT *, ’INVALID RECORD’
The above example reads in records and verifies that they contain only numeric data. The EXIT statement
is within two levels of nesting: the DO-loop and the LOOP-END LOOP structure. If a non-numeric
character is found, the EXIT : RDREC statement will cause control to be passed to the PRINT
statement after the END LOOP statement.
9.15 CYCLE
CYCLE
[ : block-label]
The CYCLE statement is used to cause a transfer of control from within a loop to the terminal statement of a
corresponding DO, DO WHILE, WHILE or LOOP statement. If block-label is present then control is
transferred to the terminal statement of the block identified by that block label.
If no block label is specified in the CYCLE statement, control is transferred to the terminal statement of the
immediately enclosing loop structure. If several loop structures are nested, it is possible to cycle to the
terminal statement of any one of them by specifying the block label of the corresponding block structure.
The CYCLE statement is most commonly used as the statement in a logical IF statement but may also be
used to cause an unconditional transfer of control.
Examples of the CYCLE statement with and without a block label follow.
210 CYCLE