Open Watcom FORTRAN 77 Language Reference

FORTRAN Statements
2.23 DO WHILE Statement
DO [s[,]] WHILE (e)
[: block-label]
where:
s
e
block-label
is an optional statement label of an executable statement, called the terminal
statement, which follows the DO statement in the same program unit.
is a logical expression or integer arithmetic expression, in which case the result
of the integer expression is compared for inequality to the integer value 0.
is an optional block label.
The DO WHILE statement is an extension to the FORTRAN 77 language.
Example:
X = 0.0
DO 10 WHILE( X .LT. 100.0 )
PRINT *, X, SQRT( X )
X = X + 1.0
10 CONTINUE
If no statement label is present, the terminal statement of the DO-loop must be an END DO statement.
Example:
X = 0.0
DO WHILE( X .LT. 100.0 )
PRINT *, X, SQRT( X )
X = X + 1.0
ENDDO
The following example illustrates the use of an integer arithmetic expression.
Example:
I = 10
DO WHILE( I )
PRINT *, I
I = I - 1
ENDDO
END
The DO WHILE statement, is similar to the DO statement. All nesting rules that apply to the DO statement
also apply to the DO WHILE statement. The difference is the way in which the looping is accomplished;
the DO-loop is executed while the logical expression of the DO WHILE statement has a true value or until
control is transferred out of the DO-loop.
For more information, see the chapter entitled "Program Structure Control Statements" on page 193.
DO WHILE Statement 53