frame namelower
file namefnameb.htm
target namelower

This is the second frame.

Divide the upper frame into two smaller frames (c & d).

This link calls a new file (fname2.htm) and places it in the upper frame. The purpose of "fname2.htm" is to take the frame named "upper" (the target) and divide it into two smaller frames. This will not disturb the original frameset definition for the upper frame nor will it remove the name that fname1.htm assigned to the upper frame. It merely divides the existing frame into two. Assume that you are now working in a new window. This is the basis for updating more than one frame at a time.
(<a href="fname2.htm" target="upper">)

This link divides the lower frame into two smaller frames (e & f).

This link calls the file (fname3.htm) and places it in this frame. It specifies two columns (e & f) at 50% each. (<a href="fname3.htm">)
Note: no target is set. The target "_self" is assumed.