A
B

File B line This grid represents all comparisons between file A and file B.
Tlines match between file A and B
      The colored cells, are the searched cells, where it searches to end of both
files, to find the path thru both files, that result in the least amount of changes. Searches occur diagonally
 search found a matching line(true)
 search covered these lines, but was fruitless
 search had to skip these lines, to find match
 search didn't bother with the work of checking those cells
  this is path returned
File A line

Assume this table means what has to be done to A, to get B