The SPD (Structured Programming Diagram) is a documentation technology used to design well structured programs. With SPD, designers can easily express functional structure, control structure, and physical layout of a program on one sheet of paper. Its straightforward expression appeals to both document writers and readers. SPD concept and conventions are introduced in this paper. SPD usage is then explained with a program design example. Other documentation technologies used in coordination with SPD are briefly touched upon. Finally, SPD reputation and evolution in the last ten years are reviewed.