Purpose
The EXIT statement
terminates execution of a DO construct or DO
WHILE construct before the construct terminates all
of its iterations. 
In addition, it can be used
to terminate execution of a specified construct
that is not DO or DO WHILE.
Syntax
Rules
If construct_name is specified, the EXIT statement must be within the construct specified by construct_name. If construct_name is not specified, the EXIT statement must be within the range of at least one DO or DO WHILE construct.
If construct_name is specified, the EXIT statement belongs to the construct specified by construct_name. If construct_name is not specified, the EXIT statement belongs to the DO or DO WHILE construct that immediately surrounds it.
If an EXIT statement belongs to a DO or DO WHILE construct, execution of the EXIT statement causes the construct to become inactive. If the EXIT statement is nested in any other DO or DO WHILE constructs, they also become inactive. Any DO variable present retains its last defined value. If the DO construct has no construct control, it will iterate infinitely unless it becomes inactive. The EXIT statement can be used to make the construct inactive.
If an EXIT statement belongs to
a construct that is not DO or DO
WHILE, execution of the EXIT statement terminates execution of the construct. Any DO or DO
WHILE loops contained within the construct become inactive.
An EXIT statement can have a statement label; it cannot be used as the labeled statement that terminates a construct.
Examples
LOOP1: DO I = 1, 20
N = N + 1
10 IF (N > NMAX) EXIT LOOP1 ! EXIT from LOOP1
LOOP2: DO WHILE (K==1)
KMAX = KMAX - 1
20 IF (K > KMAX) EXIT ! EXIT from LOOP2
END DO LOOP2
LOOP3: DO J = 1, 10
N = N + 1
30 IF (N > NMAX) EXIT LOOP1 ! EXIT from LOOP1
EXIT LOOP3 ! EXIT from LOOP3
END DO LOOP3
END DO LOOP1a : BLOCK
DO i = 1, num_in_set
IF (X == a(i)) EXIT a ! EXIT from the a BLOCK construct
END DO
CALL r
END BLOCK a