save writes data to a file as Lisp expressions. load retrieves the data written by save. Execute ? save and ? load for more information.
stringout writes data to a file as Maxima expressions. load retrieves the data written by stringout. Execute ? stringout for more information.
writefile creates a console log (a so-called "dribble" file) which records the interactions between the user and Maxima. This file cannot be reloaded into Maxima. Execute ? writefile for more information.
The functions read_matrix, read_list, read_nested_list, etc., can read files which contain numbers or symbols, arranged in rows and separated by whitespace, commas, or pipe (vertical bar) characters. write_data writes data in the same format.
These functions are in the numericalio package. load (numericalio) makes these functions available to the user.
The comments in the file share/contrib/numericalio/numericalio.lisp give more details about these functions.