Flash configuration files general questions

[Altera_Forum]

Hello all, 

 I am currently evaluting the NIOS II Dev kit Cyclone II edition and asking me some quesions about configuration files.  When we build and compile a system with Quartus, the output is a .sof file (to programm directly the FPGA) and a .pof file to program an EPCS flash as it is wrotten in the Altera's Configuration Handbook.  Well, after writing a programm using NIOS II IDE, we can use the flash programmer tool to download in the EPCS flash two .flash files : one for the FPGA design and one for the NIOS II code.  1 - What are the differences between the .flash and the .pof ?  Now comes the .rbf file. This a binary configuration file used to programm in system the EPCS flash.   2 - Is it always the .rbf file which is programmed in flash or is it really different file formats that the FPGA is able to recognize ? In other terms : Does the FPGA recognize the difference between a .pof and a .rbf file during configuration ? or is it during the flash programmation that the different programmers (SRunner, flash programmer) transforms the . flash or .pof file in order to have the .rbf programmed in flash ?  3 - Is it then possible to programm the EPCS flash with a .rbf file for the FPGA configuration and then use the NIOS II IDE flash programmer tool in order to add the NIOS II code as a .flash file ? Or do we have only the flash programmer solution to programm an EPCS flash with the FPGA configuration ans a NIOS II code ?  I am asking this because in Altera's Handbook, it's wrotten to count 850 kbytes in flash for the EP2C35 configuration file in .rbf format, the flash programmer seems to write only 280 kbytes in flash for the FPGA configuration part, the FPGA .flash file has 780 kbytes and the .pof file has 2Mbytes ????  Thank you for your answers,  Jean LEE