CD-ROM; DVD-R/W (rewritable); semiconductors; silicon wafers; integrated circuits; optical disks; recorded computer software; electronic copying machines; electronic agendas; computers; computer monitors; computer disk drives; printers for computer; computer keyboards; closed circuits; PDA (personal digital assistants); portable electronic calculators; pagers; portable communication apparatus and instruments; DVD players; MP3 players; video disk players; compact disk players; modems; headphones; television receivers; telephones; batteries; storage batteries; electric irons for ironing clothes; eye glasses; cash registers; video cameras; camcorders; telescopes; teaching apparatus using electronic circuits for use as study aids