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Glossary |
ABCP6.0 |
Accelerated Graphics Port
A dedicated graphics bus slot on PC motherboards. Designed by
Intel, AGP operates at 66 MHz and transfers data at a rate up to 528
MB/sec. By comparison, the PCI slot that most graphics cards currently
use runs at 33 MHz and has a maximum transfer rate of 132 MB/sec.
AGP's greater bandwidth will allow game and 3D application developers
to store and retrieve larger, more realistic textures in system memory
rather than video memory, without incurring a dramatic performance
hit.
basic input/output system
The BIOS is what's coded into a PC's ROM to provide the basic
instructions for controlling system hardware. The operating system
and application programs both directly access BIOS routines to provide
better compatibility for such functions as screen display. Some makers
of add-in boards such as graphics accelerator cards provide their
own BIOS modules that work in conjunction with (or replace) the BIOS
on the system's motherboard.
binary digit
A bit is the smallest unit of data in computing, with a value
of either 0 or 1. Whenever you see a lowercase b associated with a
number, it's likely to be a bit. It can be prefixed with kilo- (for
1,024 bits, or 2 to the 10th power) or mega- (1,024 x 1,024 bits)--and
sometimes finds its way into data transfer speeds (such as 14.4 kbps).
If you can read this, it's highly likely that you're using a Web browser. In brief, a browser is your interface to the World Wide Web; it interprets hypertext links and lets you view sites and navigate from one Internet node to another. Among the companies that produce browsers are NCSA Mosaic, Netscape, and Microsoft, as well as commercial services like CompuServe, Prodigy, and America Online.
A byte usually denotes 8 bits (also called an octet or a word), which the computer treats as a single unit. Longer sequences like 16 and 32 bits are also possible. Abbreviated as uppercase B.
Caches come in many types, but they all work the same way: they store information where you can get to it fast. A Web browser cache stores the pages, graphics, sounds, and URLs of online places you visit on your hard drive; that way, when you go back to the page, everything doesn't have to be downloaded all over again. Since disk access is much faster than Internet access, this speeds things up. Of course, disk access is slower than RAM access, so there's also disk caching, which stores information you might need from your hard disk in faster RAM.
compact disc, read-only memory
A compact disc used to store and play back computer data instead
of digital audio. CD-ROMs can contain up to 650MB of data (though
they often contain a lot less). CD-ROMs have become a favorite medium
for installing programs, since they cost only slightly more to manufacture
than floppy disks, and most major software applications come on at
least five floppies. Don't sound hopelessly out of touch with technology:
use the term CD-ROM to refer to the technology or the discs, but not
to the hardware you play the discs on. That's a CD-ROM drive.
A computer peripheral that plays back CD-ROMs and--with the right software--audio CDs. It consists of a spindle that revs up the disc, a laser that flashes onto the disc's uneven surface, a prism that deflects the laser beam, and a light-sensitive diode that reads the flashing light. Since the audio CD standard calls for data transfer of 150 kilobytes per second (KB/sec), all CD-ROM drives can handle this speed. There are also 24X and even 32X drives, but since most CD-ROM titles are squarely aimed at transferring data within the 2X/4X bandwidth, you'll usually not see much advantage to drives with higher transfer rates than with a 4X drive.
central processing unit
Look for the most powerful microprocessor chip in your computer,
and that'll be the CPU. The Intel Pentium and Motorola 68040 chips,
for example, handle the central management functions of a high-powered
PC and Mac, respectively. Sometimes the term CPU is used to describe
the whole box that contains the chip (along with the motherboard,
expansion cards, disk drives, power supply, and so on). Both uses
are widespread, but only the first is really accurate.
extended data-out RAM
This form of dynamic RAM speeds access to memory locations
by working on a simple assumption: the next time memory is accessed,
it will be at a contiguous address in a contiguous chunk of hardware.
This assumption speeds up memory access times by up to 10 percent
over standard DRAM.
electronic mail
Whenever you send messages to people using a computer and they
read it later, you've sent a piece of email. You can send email in
several ways--across a local area network, via the Internet, or through
an online service like CompuServe or America Online--and you can send
it to a single recipient or to a whole slew of them. But all email
behaves pretty much the same way: you send it to a virtual mailbox,
and the recipient has to pick it up or can use software that does
it automatically.
Industry Standard Architecture
Pronounced like Mr. Scott saying "Aye, sir" to Captain Kirk,
ISA is the bus design that has been used in most PCs since IBM released
the PC/AT more than a decade ago. It's a limited 8-bit and 16-bit
bus, but it's so widely compatible that it has outlasted technologically
superior--and much faster--bus standards like PCI.
Internet service provider
Once upon a time, you could only connect to the Internet if
you belonged to a major university or had a note from the Pentagon.
Not anymore: ISPs have arrived to act as your (ideally) user-friendly
front end to all that the Internet offers. Most ISPs have a network
of servers (mail, news, Web, and the like), routers, and modems attached
to a permanent, high-speed Internet "backbone" connection. Subscribers
can then dial into the local network to gain Internet access--without
having to maintain servers, file for domain names, or learn Unix.
Although kilo is Greek for a thousand, a kilobyte actually contains 1,024 bytes (that's 2 to the 10th power). In other words, a thousand bytes is actually less than a kilobyte. Remember that the next time you download a file. Abbreviated as K.
level two cache
Another term for secondary cache .
Although mega is Greek for a million, a megabyte actually contains 1,048,576 bytes (1,024 x 1,024 bytes). In other words, a million bytes is actually less than a megabyte. Remember that the next time you buy a hard disk or try to fit files onto a floppy disk. Abbreviated as MB.
megahertz A megahertz is 1 million complete cycles per second. This unit is most commomly used to measure transmission speeds of electronic devices, such as the clock speed of a microprocessor, the small computer chip that handles data-related tasks.
The microprocessor handles the logic operations in a computer, such as adding, subtracting, and copying. A set of instructions in the chip design tells the microprocessor what to do, but different applications can give instructions to the microprocessor as well. Chip speeds are measured in megahertz (MHz), so a 120-MHz chip is twice as fast as a 60-MHz chip. However, that doesn't mean your computer will run all tasks twice as fast, as speed is also influenced by other factors, such as the design of the software you're running, the operating system you're using, and so on. The first microprocessor, the 8080, was created by Intel. Other early microprocessors included Motorola's 6800 and Rockwell's 6502. The most popular microprocessors today are Motorola's PowerPC, Intel's Pentium and AMD's Athlon.
multimedia extensions In late 1996, in an effort to capitalize on the expanding market for multimedia applications, Intel unveiled an enhanced version of its Pentium microprocessor. These MMX processors contain additional instructions, or commands, and other enhancements specifically designed to handle sound, video, and graphics chores. To take advantage of MMX, software must be written specifically for these enhancements.
A modem is an external box or internal circuitry that converts computer data into sound that can be transmitted over phone lines. First used to send telegrams, early modems alternated between two different tones. This is called modulation, and the process of modulating (and demodulating at the receiving end) gave the modem its name. These days modems transmit data with lots of different tones, signals, and complex mathematical processing, so modem is a bit of a misnomer.
Monitor
Along with the keyboard and mouse, the monitor is our main link to our computers. Desktop monitors are Cathode Ray Tubes, and portable displays are Liquid Crystal Displays.
Motherboard
Every system has one: The motherboard is the largest printed circuit board in your computer. It generally houses the CPU chip, the controller circuitry, the bus, and sockets for additional boards, which are called daughterboards. If you have a horizontal-style computer, the motherboard is generally the one at the bottom of the computer's box. If you have a tower-configuration box, it's along one of the vertical sides.
OEM
original equipment manufacturer
Originally OEM was an adjective used to describe a company that produced hardware to be marketed under another company's brand. Mitsumi, for example, produced CD-ROM drives that dozens of companies would label as their own. It's often now used as a verb, as in this sentence: "This CD-ROM drive is OEM'd by Mitsumi."
PCI
Peripheral Component Interconnect
If you have a Pentium system, it's extremely likely that it runs a self-configuring PC local bus called PCI. Designed by Intel, PCI has gained wide acceptance (even by Apple, in its PowerPC series). It beats out the VESA Local Bus spec from a technical standpoint and will presumably win out in the long run. The bottom line: if you have a Pentium, make sure any add-in board you buy is a PCI device.
RAM
random access memory
Your computer should have as much RAM as you can afford if it's going to work efficiently. All computers use RAM in the same way (because they're all based on the von Neumann architecture). Both programs and data are called up from permanent storage (usually a hard drive or floppy disk) and operate in RAM. In general, this means that the more RAM you have, the more able you are to handle large amounts of data and big programs--though in practice, a lot of data in RAM is passed off into slower virtual memory to free up working space.
ROM
read-only memory
ROM is a storage chip that typically contains hardwired instructions for use when a computer starts (boots up). The instructions--contained in a small program called the BIOS (basic input/output system)--load from ROM and start up the hard disk so that the operating system (OS) can be loaded and the whole shooting match can begin. Some ROM chips can be updated with new BIOS instructions--but unless you hear them called EEPROMs or flash BIOSs, the likelihood is, they can't be.
SDRAM
synchronous dynamic RAM
Sending data from main memory to the system processor is consistently one of the biggest performance bottlenecks in any PC. Even the fastest standard DRAM and EDO memory cannot keep up with the 66-MHz bus speeds used on many Pentium systems. SDRAM incorporates new features that allow it to keep pace with bus speeds as high as 100 MHz. It does this primarily by allowing two sets of memory addresses to be opened simultaneously. Data can then be retrieved alternately from each set, eliminating the delays that normally occur when one bank of addresses must be shut down and another prepared for reading during each request.
Secondary cache
By caching data in fast, pricey memory, you speed up your system performance. A secondary cache is bigger than the primary cache (usually in the same chip as the CPU) and fits between it and main memory (RAM). It's faster than main memory, but slower than primary cache memory. It's typically around 256K in size.
SIMM
single in-line memory module
SIMMs are the most widespread form of RAM available. They're about 10cm by 2cm, and they sit in rows at either 90 degrees or 45 degrees to your motherboard. You can generally get them in 1MB to 32MB configurations.
UDMA
ultra direct memory access
UDMA defines a new protocol for the interface between the hard drive and the computer. It improves upon the ATAPI/EIDE standard by doubling data transfer rates to 33MB/sec, which translates into faster disk reads and writes. For users to take advantage of UDMA, both their system and hard drive must support the protocol. UDMA retains backwards compatibility for previously existing hardware.
USB
universal serial bus
Imagine replacing all those ports on the back of your PC--mouse, keyboard, serial, parallel, joystick, and more--with a single port. Now imagine you can daisy-chain as many as 127 peripherals off that port and use them all at once. Finally, imagine that the port supports data transfer rates up to 12MB/sec, making it suitable for even high-bandwidth applications such as video. Imagine no more. USB--designed by a consortium of PC manufacturers including Compaq, Digital, and IBM--can do all this and more. At least, it will once USB-ready systems and peripherals hit the market en masse (probably by mid-1997).