Upgrading Microcomputers 145 Maintenance and repair 100 Equipment and supplies 45 Design and construction 10 Repairing 8 Computer input-output equipment 7 Amateurs' manuals 6 High performance computing 6 Computer organization 4 Compatible computers 3 Computer games 3 IBM 3 IBM microcomputers 3 Water treatment plants 3 upgrading 3 Computer networks 2 Computer programs 2 Digital video 2 Electronic control 2 Examinations 2 Handbooks, manuals, etc 2 Home computer networks 2 IBM-compatible computers 2 Macintosh (Computer) 2 Microcomputing 2 Network computers 2 Purchasing 2 Retrofitting 2 Sewage disposal plants 2