Arithmetic constant expressions can be used in PARAMETER statements and to specify implied-DO parameters in DATA statements. All the operands in a constant expression must be literal constants or previously defined named constants. Variables, array elements, and function references are all prohibited. Exponentiation is only allowed if the number is raised to an integer power.
The same rules apply to integer constant expressions but in addition the operands must all be integer constants: such expressions can be used to specify array bounds in type, COMMON, and DIMENSION statements, and to specify string lengths in CHARACTER statements.