= = command
        .compare each line then mark the first unmatched position of the line.
        .n of xx-xxn[,b][.s] pattern is not supported
        .range by =[n] pattern and by ==-== pattern may be compared.
        .2 files on the split screen may be compared.
        .compare is done in the range of left margin for the case both files are
         margined like as SPF file.

        .ex). search unmatch postion of line 56 and 58.

               0055|#ifdef TEST
               =   |    #define MDOSDISK(fnm) (*((fnm)+1)==':' && (*(fnm)=='a'||*(fnm)=='A'&&*
               0057|#else
               =   |    #define MDOSDISK(fnm) (*((fnm)+1)==':' && (*(fnm)=='a'||*(fnm)=='A'||*
               0059|#endif

        .use of [n][,b][.s]
            (in this example,each compare pair line data is set as same)

            ==,3.1 |  A
            0002000|  B
            0003000|  C
            0004000|  D
            0005000|  E
            0006000|  F
            0007000|  G
            0008000|  H
            0009000|  I
            ==     |  J
            0011000|  K
            0012000|  L
            0013000|  M
            0014000|  N
            0015000|  O
            0016000|  P
            =,2.1  *  A
            0018000*  B
            0019000|  S
            0020000*  C
            0021000*  E
            0022000|  V
            0023000*  F
            0024000*  G
            0025000|  Y
            0026000*  I
            0027000*  J