The following program is a typical task with two input images and an output one. The easiest way to create a new task is just to start with this working template and modify what is needed.
Note that this sample task uses integer of kind=4, i.e. 32-bit numbers,
to handle some dimensions, so it will be limited to 
Gbyte data
size. Changing to kind=8 (in main program and subroutines...) would
remove this limitation.