input: Numerical data stored in machine dependent binary format, with a simple header to speed up loading. The header indicates the type of matrix as well as the number of rows and columns. For cubes, the header additionally specifies the number of slices. arma_binary is the default file_type for .save() and .quiet_save() [auto_detect] 
output: arma_binary
options: r a w _ a s c i i
options: r a w _ b i n a r y
options: a r m a _ a s c i i
options: a r m a _ b i n a r y
options: c s v _ a s c i i
options: h d f 5 _ b i n a r y
options: p g m _ b i n a r y
options: p p m _ b i n a r y