> does anyone know how to increase pic flash memory size by using external
> eeprom ? is this possible to have extended flash memory?

There is an 18 series PIC that can use external memory, but then all memory 
is external.

Most people just go and choose the next memory size up chip.

As others have noted, you can put constant data in an external EEPROM, e.g. 
strings for display on an LCD. Another option is to have the code inside the 
PIC as an interpreter, and put the tokens that get interpreted in external 
EEPROM.

You don't say just which chip you are using, or why you think you need more 
memory. 

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