The art or practice of designing computer systems. Just as the architecture of a building describes its overall structural concept and principal features, the architecture of a computer system consists of a description of the overall layout and major features of a computer system. In both cases, we are concerned with how the object, whose architecture we are describing, appears to the user. In computer architecture, the user is not the final user of the system, but the person who writes computer programs to be run on the system. Compared to the architecture of buildings, which is largely an issue of esthetics, the architecture of a computer system is principally about efficiency and economy of operation. There may be an esthetic dimension to computer architecture, but when present it is distinctly lower in importance.