Compiling Problem

I am using ide 1.6.9 and when I upload any code even from the IDE software I get an error "fork" and I can not upload anything on my board any one can help me please in this

Please post the entire error. I'm pretty sure there's more than just "fork".

1.6.9?!?

Anyway...

A bunch of people have had IDE 1.6.x problems, including IDE crashes and bizarre compile errors, when they had a previous 1.5.x/1.6.x installation. At least some of those problems seem to be caused by out-of-date executables that the IDE saves outside the IDE installation directory. Perhaps that is what is causing your particular problem. In such cases it appears that the fix is to delete or rename the old "Arduino15" directory and re-install 1.6.x.

On Mac OS X:
/Users/(username)/Library/Arduino15

On Windows:
C:\Users(username)\AppData\Roaming\Arduino15

On Linux:
/home/(username)/.arduino15 (a.k.a. ~/.arduino15)