The matrix files in MX can be divided into three components:
1) One or more (maximum 10) input .UFM files stored in the “external” memory, i.e., on the “hard disk”;
2) An “internal” matrix stored entirely in core memory (RAM);
3) A single output .UFM matrix copied (at the user's request) from the internal matrix to the “hard disk”.
These are illustrated in Figure 10.2 where the external files used for input are denoted X1, X2, etc. up to Xn, the matrix in internal memory is denoted by Y and the output matrix is Z. Thus, for example, two input matrices X1 and X2 may be added to create a new internal matrix Y which is then “dumped” to the output file Z. See 10.8.1.
By default, when one or more .ufm files are input, then initially the first input matrix is copied directly into the internal RAM. Thus the command “MX mat” would cause the matrix file mat.ufm to be read into the internal memory.
“Changes” are applied only to the internal matrix whereas the majority of “viewing” or “analysis” operations can use both internal and external files.