Open Watcom FORTRAN 77 Language Reference

Language Reference
2.53.3 IMPLICIT NONE Statement
IMPLICIT NONE
2.53.4 Description of IMPLICIT Statement
The IMPLICIT statement defines the default type and length for all variables, arrays, symbolic constants,
external functions and statement functions that begin with any letter that has appeared in an IMPLICIT
statement as a single letter or as a member of a range of letters.
The following example specifies that any name beginning with the letters A, D, E, F or G will have
default a default type of integer and any name beginning with the letters X, Y or Z will have a default type
of character and length 3.
Example:
IMPLICIT INTEGER (A,D-G), CHARACTER*3 (X-Z)
The next example illustrates the extended form of the IMPLICIT statement.
Example:
IMPLICIT INTEGER*2 (A,B), LOGICAL*1 (C-F)
IMPLICIT COMPLEX*16 (X,Y,Z), REAL*8 (P)
Specifying NONE in the IMPLICIT statement will cause Open Watcom FORTRAN 77 to issue an error
when a symbol is used and has not appeared in a type specification statement.
Example:
* Referencing X will cause an error
IMPLICIT NONE
X = 13143.383
In the above example, the IMPLICIT statement specifies that the type of all symbols must be explicitly
declared in a type specification statement. The assignment statement will cause an error since the type of X
has not been explicitly declared.
Notes:
1. The implicit type set by an IMPLICIT statement may be overridden or confirmed for any
variable, array, symbolic constant, external function or statement function name by its
appearance in a type statement. The default length specification may also be overridden or
confirmed in a type statement.
90 IMPLICIT Statement