personal watercraft (PWC), a lightweight vessel usually less than 16 ft (5 m) long that uses an inboard water jet pump, powered by an internal-combustion engine, as its primary source of propulsion. The PWC is operated by a person or persons sitting, standing, or kneeling on it, rather than inside it, as in a conventional boat. The PWC concept originated in the 1960s when a home inventor built a powered water ski that combined the elements of self-power, small size, and a maneuverable, active ride that are distinguishing characteristics of all personal watercraft. The first commercial craft, a sit-down-style PWC, was introduced in the late 1960s, but the PWC did not become commercially successful until the 1970s. Multiperson craft, carrying two, three, or four persons, are now the most common PWCs. Personal watercraft have been criticized for producing noise and air pollution, and tend more than other vessels to be maneuvered in ways that endanger the safety of other boaters. Improved engine designs, increased hull insulation, and water-safety education requirements have resulted in reduced pollution and safety improvements.

personal property: see property.

personal digital assistant (PDA), lightweight, hand-held computer designed for use as a personal organizer with communications capabilities; also called a handheld. A typical PDA has no keyboard, relying instead on special hardware and pen-based computer software to enable the recognition of handwritten input, which is entered on the surface of a liquid crystal display screen. In addition to including such applications as a word processor, spreadsheet, calendar, and address book, PDAs are used as notepads, appointment schedulers, and wireless communicators for sending and receiving data, faxes, and electronic-mail messages. Introduced in 1993, PDAs achieved only modest acceptance during the remainder of the decade due to their relatively high price and limited applications, but improved software and lower prices subsequently led to more widespread use. See also palmtop.

personal computer (PC), small but powerful computer primarily used in an office or home without the need to be connected to a larger computer. PCs evolved after the development of the microprocessor made possible the hobby-computer movement of the late 1970s, when some computers were built from components or kits. In the early 1980s the first low-cost, fully assembled units were mass-marketed. The typical configuration consists of a video display, keyboard, mouse, logic unit and memory, storage device and, often, a modem; multimedia computers add a sound-reproduction adapter, stereo speakers, and a compact disc (CD-ROM) drive to this configuration so that material can be presented in a combination of animation, graphics, sound, text, and video. Decreases in component size have made it possible to build portable PCs, or laptops, the size of a ream of paper and smaller, and palmtops, which can be held in one hand. Most current PCs have more computing power, memory, and storage than the large mainframe computers of the 1950s and early 60s. As the speed and power of the complex instruction set computer (CISC) processors used to power PCs have reached levels previously reserved for the reduced instruction set processors (see RISC processor) used in workstations, the distinction between PCs and workstations has blurred. PCs equipped with networking and communications hardware are often used as computer terminals. See also network; personal digital assistant.

Basic types of property in English common law, roughly corresponding to the division between immovables and movables in civil law. Real property consists of land, buildings, crops, and other resources, improvements, or fixtures still attached to the land. Personal property is essentially all property other than real property, including goods, animals, money, and vehicles.

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Laws passed by U.S. states in the North to counter the Fugitive Slave Acts. Such states as Indiana (1824) and Connecticut (1828) enacted laws giving escaped slaves the right to jury trials on appeal. Vermont and New York (1840) assured fugitives the right of jury trial and provided them with attorneys. Other states forbade state authorities to capture and return fugitives. After the Compromise of 1850, most Northern states enacted further guarantees of jury trials and punishment for illegal seizure. These laws were cited by proslavery interests as assaults on states' rights and as justification for secession.

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Activities that seek to minimize or to eliminate hazardous conditions that can cause bodily injury. Occupational safety is concerned with risks in areas where people work: offices, manufacturing plants, farms, construction sites, and commercial and retail facilities. Public safety is concerned with hazards in the home, in travel and recreation, and in other situations that do not fall within the scope of occupational safety.

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Political body of the French Revolution that controlled France during the Reign of Terror. It was set up in April 1793 to defend France against its enemies, foreign and domestic. At first it was dominated by Georges Danton and his followers, but they were soon replaced by the radical Jacobins, including Maximilien Robespierre. Harsh measures were taken against alleged enemies of the Revolution, the economy was placed on a wartime basis, and mass conscription was undertaken. Dissension within the committee contributed to the downfall of Robespierre in July 1794, after which it declined in importance.

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Microcomputer designed for use by one person at a time. A typical PC assemblage comprises a CPU; internal memory consisting of RAM and ROM; data storage devices (including a hard disc, a floppy disc, or CD-ROM); and input/output devices (including a display screen, keyboard, mouse, and printer). The PC industry began in 1977 when Apple Computer, Inc. (now Apple Inc.), introduced the Apple II. Radio Shack and Commodore Business Machines also introduced PCs that year. IBM entered the PC market in 1981. The IBM PC, with increased memory capacity and backed by IBM's large sales organization, quickly became the industry standard. Apple's Macintosh (1984) was particularly useful for desktop publishing. Microsoft Corp. introduced MS Windows (1985), a graphical user interface that gave PCs many of the capabilities of the Macintosh, initially as an overlay of MS-DOS. Windows went on to replace MS-DOS as the dominant operating system for personal computers. Uses of PCs multiplied as the machines became more powerful and application software proliferated. Today, PCs are used for word processing, Internet access, and many other daily tasks.

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