Open Watcom FORTRAN 77 Language Reference

Language Reference
2.5 Statement Label Assignment (ASSIGN) Statement
ASSIGN s TO i
where:
s
i
is a statement label
is an integer variable name
The statement label s is assigned to the integer variable i. The statement label must appear in the same
program unit as the ASSIGN statement. The statement label must be that of an executable statement or a
FORMAT statement.
After a statement label has been assigned to an integer variable, that variable may only be used in an
assigned GO TO statement or as a format identifier in an input/output statement. The integer variable must
not be used in any other way (e.g., in an arithmetic expression). It may, however, be redefined with another
statement label using the ASSIGN statement or it may be assigned an integer value (e.g., in an arithmetic
assignment statement).
Example:
INTEGER RET
X = 0.0
ASSIGN 100 TO RET
GO TO 3000
100 X = X + 1
ASSIGN 110 TO RET
GO TO 3000
110 X = X + 1
.
.
.
* Print both X and its square root
3000 Y = SQRT( X )
PRINT *, X, Y
GO TO RET
In the above example, we illustrate the use of the ASSIGN statement and the assigned GO TO statement to
implement a "local subroutine" in a program unit. A sequence of often-used code can be "called" using the
unconditional GO TO statement and "return" is accomplished using the assigned GO TO statement. Care
must be exercised to properly assign the return label value.
Example:
IF( FIRST )THEN
ASSIGN 100 TO LFRMT
ELSE
ASSIGN 200 TO LFRMT
END IF
WRITE( UNIT=5, FMT=LFRMT) X, Y, Z
100 FORMAT(1X,3F10.5)
200 FORMAT(1X,3E15.7)
16 Statement Label Assignment (ASSIGN) Statement