A concise history of adding machines from Schickard's 1623 device through Pascal, Leibniz, 19th-century Arithmometers and pinwheel calculators, to the electronic calculators that replaced them in the 1970s.
Dot-matrix (impact) printers form characters with tiny pins that strike an ink ribbon, enabling carbon copies and reliable printing on continuous forms. While largely replaced by inkjet and laser for general office use, impact printers remain valuable in industrial, logistics, and point-of-sale settings.
Compaq evolved from proprietary desktop systems into portable laptops under HP ownership. The shift improved compatibility and portability but introduced the industry trade-off between upgradeability and thin designs.
Compaq, founded in 1982, helped establish the IBM-compatible PC market with portable systems in the 1980s and consumer lines in the 1990s before merging into Hewlett-Packard in 2002.