The COMMON statement defines a named, shared storage area called a  COMMON
  block  or  program  section (PSECT).  BASIC program modules can access the
  values stored in the COMMON by specifying a COMMON with the same name.

  Example

  COMMON (sales_rec) DECIMAL net_sales (1975 TO 1985)

1  –  Syntax

  { COM    }
  { COMMON } [ ( com-name ) ] { [ data-type ] com-item },...

   com-item: { num-unsubs-var-name                                }
             { num-array-name ([int-const1 TO] int-const2,...)    }
             { str-unsubs-var-name = int-const                    }
             { str-array-name ([int-const1 TO]
               int-const2,...) [=int-const]                       }
             { FILL [(int-const)] [=int-const]                    }
             { FILL% [(int-const)]                                }
             { FILL$ [(int-const)] [=int-const]                   }