IMPLICIT NONE statement
Standard: F77 F90 F95 F2003
<Syntax>
IMPLICIT NONE statement

The IMPLICIT NONE statement must be the first declaration following any USE or IMPORT statements.
<Semantics>
The IMPLICIT NONE statement sets the implicit type mapping for every letter to null, so there are no implicit types. This means that all variables and functions must be explicitly typed.
<Related>
IMPLICIT statement