To declare the minimum value for array subscripts.
OPTION BASE n
n is 1 or 0. The default base is 0.
If the statement OPTION BASE 1 is executed, the lowest value an array subscript can have is 1.
An array subscript may never have a negative value.
OPTION BASE gives an error only if you change the base value. This allows chained programs to have OPTION BASE statements as long as the value is not changed from the initial setting.
You must code the OPTION BASE statement before you can define or use any arrays. If an attempt is made to change the option base value after any arrays are in use, an error results.