I am trying to make a multithreaded QT GUI application.
I have 3 files :
main.cpp
mainwindow.cpp
grabthread.cpp
there are 2 header files:
mainwindow.h
grabthread.h

I want to declare an array of the size 1200*5000 globally so that it is accessible in all 3 files.

I have tried declaring it :
1> before main() in main.cpp (using extern also)
2> in mainwindow.cpp
3> in mainwindow.h

but I am unable to access the array in other files.
Where should i declare the array? So that i have global access