How i know wear is already define symbol ?

Its not simple when i using many files\includes in my program.

And i want know wear is (in file) exist already defined symbol.
Or how get num line in code ?

A quick hack that allows to find out: put the definition of such named symbol in the first line of source. Then the assembler is going to show you the error on a next definition, which was previously the first one.

Also, if I recall correctly, Fresh has a feature of going to the definition of symbol on demand. Or you could use the "symbols" .fas converter that comes with fasm in "tools" directory.

Not that I consider it needless to have more information in the original error message, but cases like this were never a priority to me.

I use NotePad++
Find in files !
Very helpful.