ESRI World File Format(.tfw)

The ESRI World format stores the image-coordinates-to-world-coordinates transformation data resulting from the georeferencing process executed in the Map Assistant.
The resulting file contains the transformation factors A to F defining the registering of the image in accordance with the equation below:

 

1. x' = A x + B y + C

    

2. y' = D x + E y + F

with x,y = Image coordinates     x',y'= Real world coordinates     A = x-scale     B,D = rotation terms     C,F = translation terms     E = y-scale (negative)     

Example for a .tfw file:

    4.23214625853148 - A    0.00000000000000 - D    0.00000000000000 - B   -4.23214625853148 - E    3404018.70881921 - C    5819863.55539414 - F

From:http://geos.gsi.gov.il/vladi/FEFLOW/help/general/file_format.html#tfw_file