Digital Equipment Corporation
Hardware
Littleton, MA    June 1991--August 1991

C++, X Window System, Unix

Digital Equipment Corporation is a leading worldwide supplier of networked computer systems, software, and services. Digital has built strategic alliances with customers, value-added resellers, independent software vendors, systems integrators, and other computer vendors to address the needs of a rapidly changing marketplace. Digital does more than half its business outside the United States, developing and manufacturing products and providing customer services in the Americas, Europe, Asia, and the Pacific Rim.

XFlowgraph is an X application displaying the flow chart of an executable for the Alpha chip. Its input comes from a machine code translator, which converts machine code from one platform to machine code for the Alpha. XFlowgraph originated in the early days of the DEC's Alpha project, as part of a migration solution for customers with a large installed software base on other platforms.

XFlowgraph was originally written in C++, purely using Xlib as the user interface. (This includes common GUI elements such as scrollbars and buttons.) Main responsibilities were to convert the Xlib code to a common toolkit and add new user interface features. Resulting changes to the application were as follows:

	Rewrote all Xlib GUI code to use the Xt toolkit and the Athena Widget set (Xaw), using standard button and scrollbar widgets for common GUI elements, and creating a new widget for the main XFlowgraph display window
	Completely rewrote all other Xlib drawing code for efficiency reasons. Resulting code yielded dramatic performance improvements, from 100% to 500% depending on the X server
	Added many new commands and GUI features to the application

It should be noted that C++ and X were new technologies at the start of this summer position. However, completely unaided save for a couple of C++ and X manuals, within three months most of the application had been completely redesigned and rewritten. This involved thoroughly learning C++, Xlib, Xt, and Xaw to write new classes, write a new widget, rewrite much Xlib code in Xt and Xaw, use Xaw for new functionality, and completely redo the remaining Xlib code to improve performance.