Hi, I need to declare a large multiarray in a multi-class project, something in the order of 10,000 x 300 x sizeof(a struct of 48 byte), I need to put the matrix in a header file so that other classes can see it. would it be a good idea to put all of the following lines in a header file? or the memory allocation should really be done in a .cpp file while leaving a pointer of some sort in the header? in other words, what would be a better way of declaring a large multiarray in a multi-file project? typedef boost::multi_array xyType; //xystruct is a struct of 6 doubles xyType xy(boost::extents[10000][300]); many thanks mike