Fundamentals of Statistics contains material of various lectures and courses of H. Lohninger on statistics, data analysis and here for more.

Zero Matrix

A zero matrix (or null matrix) is a matrix with all its elements being zero; it is denoted by the symbol 0 (zero).

When adding a zero matrix to another matrix A the matrix A stays unchanged. The multiplication of matrix A with a zero matrix results in a zero matrix (which may be of different order, however).