Partition table confusion

["Steve Dondley" <s@dondley.com>]

Hi,

I'm trying to learn as much as possible about the logical structures on a
hard disk.  I was looking at cfdisk's printout of my partition table and I'm
a little confused by it:


         ---Starting---      ----Ending----    Start Number of
 # Flags Head Sect Cyl   ID  Head Sect Cyl    Sector  Sectors
-- ----- ---- ---- ---- ---- ---- ---- ---- -------- ---------
 1  0x80    1    1    0 0x83  239   63 1023       63  19867617
 2  0x00  239   63 1023 0x05  239   63 1023 19867680    136080
 3  0x00    0    0    0 0x00    0    0    0        0         0
 4  0x00    0    0    0 0x00    0    0    0        0         0
 5  0x00  239   63 1023 0x82  239   63 1023       63    136017


Based on the ID field, Entry #1 is the regular linux partition and entry #2
is the swap partition.  My questions are:

What is Entry #2?  It's ID is 05 which is an extended DOS partition.
However, when I set up my hard drive, I never created this partition.  How
did it get there?

How can partition #2 and partition #5 share the same start and end h,s,c
number yet have such different start sectors (I'm assuming the 19867680 is
LBA)?

I thought partition tables could only have 4 entries.  This table shows 5.
Why?

Any insight on these questions is greatly appreciated.