Lisp machines are general-purpose computers designed to efficiently run Lisp as their main software language, usually through hardware support. They are an example of a high-level language computer architecture, and in a sense, they were the first commercial single-user workstations. Despite being modest in number (perhaps 7,000 units total as of 1988), Lisp machines commercially pioneered many now-commonplace technologies – including effective garbage collection, laser printing, windowing systems, computer mice, high-resolution bit-mapped graphics, computer graphic rendering, and networking innovations like Chaosnet. Several companies built and sold Lisp Machines in the 1980s: Symbolics (3600, 3640, XL1200, MacIvory, and other models), Lisp Machines Incorporated (LMI Lambda), Texas Instruments (Explorer and MicroExplorer), and Xerox (Interlisp-D workstations). The operating systems were written in Lisp Machine Lisp, InterLisp (Xerox), and later partly in Common Lisp.