paper chromatography (PC)
Type of chromatography using filter paper or other special paper as the stationary phase. Spots of sample and reference materials are applied, usually as liquids, near one edge (or corner, for two-dimensional PC) of the paper. The edge of the paper is dipped in a solvent, which travels along it by capillarity, moving the components of the sample at rates depending on their relative solubilities in the solvent. In two-dimensional PC, the paper is then turned 90° and the new edge dipped in a different solvent. The components of the sample mixture, visible as separated spots, are identified by comparing the distances they have traveled with those of the known reference materials. PC is especially useful for complex mixtures of amino acids, peptides, carbohydrates, steroids, and many other organic compounds and inorganic ions.
personal computer (PC)
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.
PC
(1) See printed circuit board and phase change.
(2) (Personal Computer) Any laptop or desktop computer such as a Windows, Macintosh or Linux machine.
(3) (Personal Computer) In contrast to the more generic definition above, PC typically refers to an x86-based desktop or laptop computer, almost all of which run under Windows. PC hardware and operating systems are primarily governed by Intel and Microsoft; however, there are numerous other strong influences. The PC represents the world's largest computer base. More than a billion of them are connected to the Internet, with shipments of new PCs exceeding a quarter million units per year.
PCs are sold by large vendors such as HP and Dell, as well as by thousands of small and large computer dealers who assemble them from standard parts. Ironically, IBM launched the PC in 1981 and exited the business in 2004, selling its PC division to Chinese-based Lenovo.
PC Clients and Servers
The term PC typically refers to the user's desktop or laptop computer, which is called a "client" machine. However, x86-based machines are also widely used for servers, running server versions of Windows such as Windows 2000 and Windows Server 2003, as well as Linux, Unix and other operating systems. See x86-based system.
The IBM PC
IBM launched the PC in 1981, and competitors immediately tried to create PC clones. Except for Compaq, most attempts failed until 1985, when the BIOS chip in the PC was successfully cloned and made available to others. From then on, true compatibles were made by numerous vendors, and the PC industry was established.
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| What's Inside a PC |
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| In today's PC (bottom), most plug-in cards (vertical cards) are absent, as the majority of I/O functions typically reside in a chipset on the motherboard (see PC chipset). The single CD-ROM drive gave way to a DVD drive that supports all CD read and write functions, and floppy drives are obsolete. Computers designed for gamers and other graphics-intensive operations have a separate, high-end display adapter card and may possibly have a separate sound card. |
PC
| 1. | (computer) | PC - personal computer. | |
| 2. | (computer) | PC - IBM PC. | |
| 3. | (hardware) | PC - program counter. | |
| 4. | (hardware) | PC - printed circuit. | |
| 5. | (language) | PC - Parallel C. |
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