= Tab display

        TAB {on | off | clear | =default | nn [asdefault] }
            on      :display tab char and DBCS(Japanese) space.
                     Char used to display tab and its following space
                     is customaizable by .INI file parameter.
                     Default is Tab       :Up-arrow
                                Tab-skip  :Right arrow
                                DBCS space:shadow box
            off     :tab char is not displayed.
                     Special char for un-displayable char
                     is always displayed regardless this option.
            clear   :remove tab with space remained.
            =default:set this file's tabctr to the default setting.
            nn      :Tab column interval,default is 4.
                     With "asdefault", set default tabctr.
                     Without "asdefault", set the tabctr of currentry opened
                     and profile record is updated.
                     Tab key cause cursor jump not to next tab column
                     but jump to next field when default tab column is 0.
                     Maximum 12.
                     1 is forced to the file opened by record mode.