M - its dimension
G - a double dimension array  G(M,N) or GX(M,N)
N - the second dimension (M is first)
N=0 => G is vector G(M)
N=1 => G is lower diag half of M*M symmetric matrix
N>1 => G(M,N)
INSERT - page code; =1 start a new page
LABEL - optional label for matrix
NLABEL - number of bytes in label; >1 => print the label