Each workstation vendor offers its own windowing systems and graphics library. Even though skills and codes developed on one graphics workstation usually transfer to another fairly easily, this transfer can sometimes be tedious and time consuming. Unless one requires some hardware or software feature that is vendor specific, the issue of skill and code transfer can often be avoided. X-Windows provides a ``standard'' environment that is common to a broad range of UNIX workstations. To the software end user, the X-Window environment is portable and robust and provides access to a large number of high quality, public domain visualization software packages. In addition, the X11 library contains functions that enable a computational scientist to manage windows and to develop custom graphical interfaces.
In many universities and laboratories there are not enough seats at UNIX graphics workstations to meet everyone's needs. For those scientists who are developing custom visualization software, a PC (Macintosh or IBM clone) equipped with at least VGA quality graphics has proven to be a valuable tool in combating a shortage of workstations. Much of the early design and ``proof of concept'' testing can be done on the PC. With the advent of PCs with several megabytes of memory and with increased graphics resolution, such as the SVGA at 1024x768 pixels, the modeler can now use a DOS based PC to perform many of the tasks of the UNIX workstation.