The C64 is based on a MOS 6510 processor, with 64K of RAM standard. It can display up to 40 columns and 25 lines of text with 16 colors on-screen. Almost every program runs at a standard 320×200 resolution. Furthermore, game development is aided by built-in “sprite” capabilities, which simplify and standardize the basic graphic and animation routines used by most games. Perhaps more impressive still is the C64’s sound output, powered by a professional synthesizer chip called SID (Sound Interface Device). SID enables three voices (channels) at nine octaves and four waveforms; enough power for serious electronic music. The C64 offered superior graphics and sound to rivals machines such as the Apple II, and came with a cheaper price tag and larger software library. For a substantial period (1983–1986), the C64 had between 30% and 40% share of the US market and two million units sold per year, outselling IBM PC compatibles, Apple computers, and the Atari 8-bit family of computers. The C64 holds the record of being the best-selling single personal computer model of all time. Between 20 million and 30 million units are sold worldwide over its 12-year production period and more than 10,000 commercial software titles were released.