REAL :: m=4, n=2, p=3, a(m,n), b(n,p), res(m,p)

a = $ ! initialize to 1, 2, ..., m*n
b = $ ! initialize to 1, 2, ..., n*p

res = 0
DO i = 1, m
  DO j = 1, p
    DO k = 1, n
      res(i,j) = res(i,j) + a(i,k) * b(k,j)
    ENDDO
  ENDDO
ENDDO

DLG(DefWidth=4, Text=a, Text=b,Y=0, Text=res,Y=0)