Hewlett-Packard, often referred to as just 'HP', is a US corporation with its headquarters in Palo Alto, California. It was started in 1939 by two Stanford engineering graduates called Bill Hewlett and Dave Packard, famously in Packard's garage. The order of their surnames in the company name was determined by the toss of a coin (which Packard won, who then chose the name).
Initially the company developed and sold electronic test equipment. In 1972 they launched the HP-35, the world's first handheld scientific calculator, followed in 1974 by the breakthrough HP-65 which was the first programmable pocket calculator.
HP calculators have been the tool of choice in the engineering and scientific professions because of their quality of construction, particularly the characteristic design and feel of the calculator keys, and technology leadership. They have mostly continued to use reverse polish notation (RPN) which has set them apart from other manufacturers products, and have made a market differentiating virtue out of what was originally a technological necessity.
Over the years HP began to build computers and peripherals which eventually became their mainstream business. But they have continued to manufacture calculators, despite many rumours to the contrary in more recent years. Admittedly the manufacturing of many models is now outsourced, and the reputation for heroic build quality has consequently suffered.
More information can be found at http://www.hp.com/, the Hewlett-Packard corporate website.
Calculators made by Hewlett-Packard