Note: unless otherwise specified, all performance numbers in this chapter are for programs compiled with the GNU gcc compiler version 2.5.8 using optimization option -O, on a Dell Model XPS90 with an Intel 90Mhz Pentium processor, 256KB 4-way associative L2 cache memory, and 16MB of RAM. This machine was running the Slackware distribution of Linux (kernel version 1.1.59), a freely distributable UNIX-compatible operating system. Where file I/O was performed, local disk storage was used; where the programs being run were memory-intensive, all unnecessary processes (including X Windows) were terminated to make the amount of memory free (approximately 12MB, as reported by the Linux free utility) reproducible. No other users were logged in consuming machine resources; the machine does not provide any network services of note.