T-V

tab

A graphical depiction of the tab on a paper file folder. Click a tab to select a different page in a dialog box or property sheet. Sometimes used to represent the entire page that a tab is on.

TB (Terabyte)

1,024 gigabytes, approximately 1 million megabytes, or 1,099,551,627,776 bytes.

TCP/IP (Transmission Control Protocol/Internet Protocol)

The primary set of protocols used by the Internet and most networks. TCP/IP allows different networks and computers to communicate with one another.

text-based interface

Interface that involves typing commands rather than using graphical elements. Contrast with GUI. Synonym: command-line interface.

throughput

Measurement of the speed of data transfer.

toggle

Turn a software or hardware element on or off. For example, pressing the <Caps Lock> key on the keyboard toggles uppercase letters on or off.

touchpad

A flat pointing device that works by sliding a fingertip across its surface. Software can provide additional features such as tapping to click. Synonym: trackpad.

trackball

A pointing device that has a partially enclosed ball that the user rolls to move the pointer.

trackpad

See touchpad.

TSR (Terminate-and-Stay-Resident Program)

A program that remains resident in computer memory and can be run repeatedly without having to be reloaded into memory. Most TSR programs are loaded into memory by the DOS file AUTOEXEC.BAT. DOSKEY is a TSR program.

UART (Universal Asynchronous Receiver/Transmitter)

A chip that converts data from serial information to parallel information, and vice versa. UARTs are used for equipment or devices that are attached to serial ports.

UMA (Upper Memory Area)

The first 640K to 1024K of memory addresses reserved for device drivers and system use.

UMB (Upper Memory Block)

A reserved memory block in the UMA used to load device drivers and TSR programs.

UPS (Uninterruptible Power Supply)

Provides a continuous supply of power to a computer system when a primary power source fails. A UPS can also protect a system from power sags. It is indispensable when making changes to a computer’s BIOS, because a power failure during a BIOS update will render a computer useless unless a replacement BIOS chip is obtained and installed, which isn’t always possible. UPSs almost always include surge suppression. Synonym: battery backup.

URL (Uniform Resource Locator)

A URL is an address that points to a resource or another URL located on the World Wide Web. An example of a URL is http://www.charlesriver.com.

USB (Universal Serial Bus)

An interface standard that supports up to 127 devices using one system resource (IRQ). With USB, PnP peripheral devices can be attached to a computer system while the power is on and the operating system is up and running. Only the USB controller uses IRQs or other Device Manager resources; the connected devices don’t.

Usenet

A system of communication on the Internet in which subscribers to newsgroups can post and reply to messages that all subscribers can see.

UTP (Unshielded Twisted Pair)

A common type of twisted-pair cable used in most networks. There are five categories of UTP that support different data transmission speeds. Unlike STP, UTP does not have a protective shielding.

VGA (Video Graphics Array)

See SVGA.

video card

A device whose primary function is to generate a video signal (“picture”) to be shown on the monitor. A video card can either be a separate card that plugs into a slot on the motherboard, or a device built into the motherboard. Synonyms: video adapter, graphics adapter, display adapter.

virtual memory

System used by Windows that uses hard disk space as additional memory in a process called paging. The file where Windows stores virtual memory data is called the page file or the swap file.

VL-Bus (VESA local bus)

A 32-bit expansion bus that has been replaced by PCI expansion bus technology.

voltmeter

A device that tests only the voltage of a circuit.

VPN (Virtual Private Network)

A way to provide secure network access to the individual users and remote offices of an organization without the excessive expenses associated with owning or leasing the lines. This is done via the Internet by using a shared public infrastructure and tunneling. Additional security features can be utilized to enhance privacy.

VRAM (Video Random Access Memory)

A special type of dual-ported memory that is used in video adapters to produce graphic images on a computer monitor.

VRM (Voltage Regulator Module)

A small, replaceable module that is installed on the motherboard to sense the microprocessor’s voltage requirements and regulate the voltage fed to the microprocessor. Nearly all motherboards have either a built-in voltage regulator or VRM. Therefore, if the computer’s microprocessor is changed, a VRM may need to be added to the existing voltage regulator to keep consistent with the voltage requirements of the new microprocessor.

VxD (Virtual Device Driver)

A 32-bit device driver used in Windows. Virtual device drivers have a .VXD extension.