... This paper describes our application of the X Public Access ( XPA ) interface to the new version of SAOimage . XPA allows an Xt program to define named public access points through which data and commands can be exchanged with external programs. ... It provides a high-level image display programming interface as well as low-level access to gterm-image widget functions. ... When a new file name is sent to SAOtng , the appropriate header access program is run to gather the overall image dimensions. ...