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V.34 standard A communications (modem) standard that transmits at 28,800 bps and/ or 33,600 bps.

 V. The CCITT international communications standards, pronounced "vee-dot." Various V. standards cover speed (modulation), error correction, data compression, and signaling characteristics.

Value data In Windows 95 and NT, the name and the value of a setting for a key in the registry.

VAR (Value Added Reseller) A company which resells hardware and software packages to developers and/or end-users.

VCACHE A built-in Windows 95 32-bit software cache that doesn't take up conventional memory space or upper memory space, as SmartDrive does.

VDD or VxD drivers (Virtual device drivers) Programs that emulate the DOS device drivers for hardware devices in Windows 95 and Windows NT.

Vector table See I/O address table.

VESA (Video Electronics Standards Association) VL bus A bus used on 80486 computers for connecting 32-bit adapters directly to the local processor bus.

Vertical frequency This is also called the vertical refresh rate, or the vertical scan frequency. It is a monitor term that describes how long it takes to draw an entire screenful of lines, from top to bottom. Monitors are designed for specific vertical and horizontal frequencies. Vertical frequency is a key factor in image flicker. Given a low enough vertical frequency (53 Hz, for example) nearly everyone will see a flicker because the screen isn't rewritten quickly enough. A high vertical frequency (70 Hz on a 14-inch monitor) will eliminate the flicker for most people.

VFAT (Virtual file allocation table) A variation of the original DOS 16-bit FAT that allows for long filenames used in Windows 95.

VGA IBM's third (1987) and current mainstream graphics standard, capable of 640-by-480-pixel resolution at 16 colors or gray shades. SuperVGA (800 by 600) resolution is important on desktop PCs. A handful of laptops support SuperVGA when connected to an external monitor; they use regular VGA when driving the built-in display. Some laptop vendors use "text mode" VGA, which means the monitor displays only 400 pixels, not 480, vertically, and uses double-scan CGA (640 by 400) for graphics.

Video card An interface card installed in the computer to control the monitor.

Video controller card A card installed in the computer that controls the monitor. Another name for display adapter.

Video driver A program that tells the computer how to effectively communicate with the video adapter card and monitor. It is often found on a disk that is shipped with the card.

Video memory Microchips on the video card that hold the data that is being passed from the computer to the monitor. Higher resolution often requires more video memory.

Video RAM or VRAM RAM on video cards that allows simultaneous access from both the input and output processes.

Video-capturing card A multimedia card that can capture input video and convert the frames into motion files or still clips that can be stored on disk.

Virtual memory Hard disk space used as though it is RAM in order to increase total RAM in a system. Because hard drives are much slower than RAM access, virtual memory is relatively slow.

Virtual Memory Manager A Windows 95 or NT program that controls the page table, swapping 4K pages in and out of physical RAM to and from the hard drive.

Virus A program that often has an incubation period, is infectious, and is intended to cause damage. A virus program might destroy data and programs of damage a disk drive's boot sector.

Virus signature The distinguishing characteristics or patterns of a particular virus. Typically, AV signature updates for new viruses can be downloaded monthly from the Internet.

VM (Virtual machines) Multiple logical machines created within one physical machine by Windows, allowing applications to make serious errors with out disturbing other programs.

Volt A measure of the potential generated by "pressure." One volt is the potential generated by 1 ampere of current flowing through 1 ohm of resistance. A computer power supply usually provides four separate voltages: +12V, -12V, +5V, and -5V.

Voltmeter A device for measuring electrical voltage.

Voltage A potential diffrence in electrical "pressure" that causes current to flow, measurde in volts. (See Volts.)

VRAM (Video Random-Access Memory) Special-purpose RAM with two data paths for access, rather than the one path in conventional RAM. The two paths let a VRAM board handle two functions at once: display refresh and processor access. VRAM doesn't force the system to wait for one function to finish before starting the other, so it permits faster operation for the video subsystem.

VRM socket (Voltage regulator module) Converts the system power supply voltage to the voltage required by the CPU.