The text and heading fonts are ITC Garamond Light and Garamond Book. The illustrations that appear in the book were created in Macromedia Freehand 5.0 by Chris Reilley. The animal featured on the cover of Pthreads Programming is a silkworm. Silkworms produce silk when they secrete a fine, strong filament while spinning their cocoons. According to legend, the Empress Ling-chi discovered how to unwind the filament approximately 3000 years ago B.C., and thus produced the world's first silk fabric.
Silkworms survive exclusively on certain strains of mulberry leaves.
The cultivated silkworm no longer exists in the wild. Although silkworms have been cultivated on a relatively small scale elsewhere, few places have both the warm climate and the abundance of mulberry trees that silkworms require, and so Asia, specifically China, continues to be the main producer of silk.