Open Watcom FORTRAN 77 Language Reference

Program Structure Control Statements
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’ )QUIT : 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 QUIT statement
is within two levels of nesting: the DO-loop and the LOOP-END LOOP structure. If a non-numeric
character is found, the QUIT : RDREC statement will cause control to be passed to the PRINT
statement after the END LOOP statement.
9.14 EXIT
EXIT
[ : block-label]
The EXIT statement is used to transfer control:
1. from within a loop (DO, DO WHILE, WHILE or LOOP) to the statement following the loop,
2. from within a GUESS or ADMIT block to the statement following the ENDGUESS statement, or
3. from within a remote block to the statement following the EXECUTE statement that invoked the
remote block.
When transferring out of a loop, control is passed to the statement following the END DO, END WHILE,
END LOOP or UNTIL statement.
When transferring out of a GUESS block, control is passed to the statement after the corresponding END
GUESS statement.
When transferring out of a REMOTE-block, control passes to the statement following the EXECUTE
statement that invoked the REMOTE-block.
If no block label is specified in the EXIT statement, control is transferred from the immediately enclosing
structure. If several structures or DO-loops are nested, it is possible to exit from any one of them by
specifying the block label of the corresponding block structure.
The EXIT statement is most commonly used as the statement in a logical IF or AT END statement but
may also be used to cause an unconditional transfer of control. (The AT END statement is described in a
subsequent section).
Examples of the EXIT statement with and without a block label follow.
EXIT 209