The normal - and extremely easy and effective - method of numbering your
ancestors is to assign yourself (or child) the number 1. If you are No. 1,
then your father is No. 2, your mother No. 3, your paternal grandfather No.
4, etc. In this system, a person's father's number is always twice the
person's number and his or her mother's number is twice plus one. Decimal
points are added for side branches of the family. This method of numbering
one's ancestors is used worldwide and is called the Sosa-Stradonitz
System for the Spanish genealogist Jerome de Sosa who first used it in
1676 and for Stephan Kekule von Stradonitz who popularized it in his 1896
Ahnentafel Atlas. It is also sometimes called the "Ahnentafel Numbering
System."  Ahnentafel is a German word meaning 'ancestor table'.  Other
than the starting person, males always have even numbers  and women
odd numbers, and children of any of these couples who are not in Person Number one's direct ancestry are given the number of their father with a
decimal point and a number relating to their birth-order among their
siblings. The ID number of a spouse is appended with the letter "s".  For example:

     1    Rebecca Ann Hall
     2    Horace Marvin Hall
     3s  Nellie L. Lorren
     4    Unknown
     5s  Alma Dudley
     6    Jasper Tillman Lorren
                3      Nellie L. Lorren
                6.2.  Kenneth Lorren
                6.3   Clarence D. Lorren
     7s  Christine Inez Cook (Lorren)
     8    Unknown
     9s  Unknown
    10   Unknown
    11s Unknown
    12   Samuel Prathel Lorren
              6 Jasper Tillman Lorren
    13s  Nancy Olena Hedgepeth (Lorren)
    14    Franklin Cook
    15s  Georgia Haney (Cook)

If the same information was presented as a pedigree, it would look
something like this:

                                                 8. Unknown
                              4. Unknown
                              |                  9. Unknown
                              |
               2. Horace Marvin Hall
               |              |                  10. Unknown
               |              5.  Alma Dudley
               |                                 11. Unknown
1. Rebecca Ann Hall
               |
               |                                 12. Samuel Prathel Lorren
               |              6. Jasper Tillman Lorren
               |              |                  13. Nancy Olena Hedgepeth
               3. Nellie L. Lorren

                              |                  14. Franklin Cook
                              7. Christine Inez Cook
                                                 15. Georgia Marilyn Haney

Notice that the numbers are the same as in the ahnentafel if you read the
pedigree left to right and top to bottom. The advantage of the pedigree is
that it gives a nice visual view of the relationships. But the ahnentafel can
show a lot more information in a concise way. It is also easy to add
additional information (dates and places of birth, death and marriage;
biographical info, etc.) to an ahnentafel.