= o command
         .only overwrite method is different with "p" command.
          p cmd:paste all chars of the source line.
          o cmd:only space chars of destination line are overwritten
                by char of corresponding position of source line.
          n cmd:only non-space char of source line are selected
                and overwrite correspondiong postion of destination line.


            c      |  :  :  :
            oo     |02/11/05
            0003000|01 23 51 123
            0004000|01 23 55 228
            0005000|01 24 12 560
            0006000|02 13 01 125
            0007000|02/11/06
            0008000|01 14 12 160
            oo     |02 16 01 225
        ===>
            0001000|  :  :  :
            0002000*02/11/05:
            0003000*01:23:51:123
            0004000*01:23:55:228
            0005000*01:24:12:560
            0006000*02:13:01:125
            0007000*02/11/06:
            0008000*01:14:12:160
            0009000*02:16:01:225
            0007000*03:03:34.970