Open Watcom FORTRAN 77 Language Reference

Language Reference
The next example demonstrates the use of a GO TO statement to control execution of all or part of a
DO-loop.
Example:
I = 1
DO WHILE( I .LE. 3 )
J = 1
DO WHILE( J .LE. 5 )
PRINT *, ’INNER LOOP - J=’, J
IF( J .LE. 3 )GO TO 20
PRINT *, ’J > 3’
20 END DO
PRINT *, ’OUTER LOOP - J=’, J
END DO
A result of this example is that the character string J > 3 is printed 6 times (i.e., twice for each iteration
of the outer loop). Of course there is a much better way of coding this algorithm using the IF-END IF
construct. The example is included to illustrate the behaviour of transfers of control to an END DO
statement. The following example is an equivalent algorithm to the one above but the intent is much
clearer.
Example:
I = 1
DO WHILE( I .LE. 3 )
J = 1
DO WHILE( J .LE. 5 )
PRINT *, ’INNER LOOP - J=’, J
IF( J .GT. 3 )THEN
PRINT *, ’J > 3’
END IF
END DO
PRINT *, ’OUTER LOOP - J=’, J
END DO
9.6 LOOP - END LOOP
LOOP [: block-label]
statement(s)
END LOOP
This extension to FORTRAN 77 causes the statements between the LOOP and END LOOP statements to be
repeated until control is transferred out of the loop, usually by an EXIT or QUIT statement. An optional
block label may be specified (see the CYCLE, EXIT or QUIT statement for more information). An
example follows:
198 LOOP - END LOOP