                               The ECX Register

Called the Counter.


Graphical Breakdown:

      [       16 bits       |    8 bits    |   8 bits    ]
                                   CH            CL
                                          CX
                           ECX

ECX is a 32 bit register that is broken down into:
CX - The Low 16 bit half
CH - High 8 Bits of CX
CL - Low 8 Bits of CX

ECX register is available from the 80386+.  CX/CH/CL are available
on all 80x86 processors.

This register is usually used for counting, and commands like LOOP
and REP* (Where * is NE, NZ, etc) use ECX/CX as an implied
operand based on if ECX/CX is 0 or not.

Other Information:


On startup in a .COM in real mode:

ECX = ????
CX = 255 (0FFh)
CH = 1
CL = 255 (0FFh)

(These values should NOT be used in general programming.  But, if you are
 coding for optimization and the application does not really matter that 
 much, in DOS you can almost count on these values.  Although, I wouldn't
 be tring to run them on DOS EMUs like OS/2, which the startup values
 may be differnt.  A lot of demo coders count on these values in making
 their demos a little smaller, although it is a portability issue if they
 will run on all systems.)
