A B C D E F G H I J K L M N O P Q R S T U V W X Y Z.

(V)

V90: V.90 is a standard, approved by the International Telecommunications Union (ITU), for transmitting data downstream to modems at 56 Kbps (thousand bits per second). The V.90 standard was arrived at by combining the x2 technology from US Robotics (now part of 3Com) and the K56flex technology from Rockwell. Transmission upstream from a computer modem is slower than downstream (about 33 Kbps) since it requires digital-to-analog conversion.
56 Kbps transmission technologies exploit the fact that most telephone company offices are interconnected with digital lines. Assuming your Internet connection provider has a digital connection to its telephone company office, the downstream traffic from your local Internet access provider can use a new transmission technique on your regular twisted-pair phone line that bypasses the usual digital-to-analog conversion. A V.90 modem doesn't need to demodulate the downstream data. Instead, it decodes a stream of multi-bit voltage pulses generated as though the line was equipped for digital information. (Upstream data still requires digital-to-analog modulation.)
Unlike ISDN, the 56 Kbps technologies do not require any additional installation or extra charges from your local phone company. On the other hand, the maximum transmission speed of ISDN is twice that of V.90 at 128 Kbps. You also have the flexibility of combining digital and voice transmission on the same line.

VERONICA: Veronica is a program that allows you to search the files of the Internets Gopher servers for a particular search string. Like Archie, Veronicas equivalent program for FTP servers, Veronica is an indexing spider that visits the Gopher sites, reads all the directory and file names, and then indexes them in one large index. A user can then query Veronica, which checks the query against its index. To use Veronica, you can Telnet or link through your Web browser to a server that you know has Veronica on it and then enter search commands.
Veronica and Archie are perhaps of most use for serious researchers who have already tried the Webs main search engines first or who already know that the topic of their search is likely to be found on Gopher and FTP servers.

VIRUS: A virus is a piece of programming code inserted into other programming to cause some unexpected and, for the victim, usually undesirable event. Viruses can be transmitted by downloading programming from other sites or be present on a diskette. The source of the file you are downloading or of a diskette you have received is often unaware of the virus. The virus lies dormant until circumstances cause its code to be executed by the computer. Some viruses are playful in intent and effect ("Happy Birthday, Ludwig!") and some can be quite harmful, erasing data or causing your hard disk to require reformatting.
Generally, there are three main classes of viruses:
File infectors. These viruses attach themselves to program files, usually selected .COM or .EXE files. Some can infect any program for which execution is requested, including .SYS, .OVL, .PRG, and .MNU files. When the program is loaded, the virus is loaded as well.
System or boot-record infectors. These viruses infect executable code found in certain system areas on a disk. They attach to the DOS boot sector on diskettes or the Master Boot Record on hard disks. A typical scenario (familiar to the author) is to receive a diskette from an innocent source that contains a boot disk virus. When your operating system is running, files on the diskette can be read without triggering the boot disk virus. However, if you leave the diskette in the drive, and then turn the computer off or reload the operating system, the computer will look first in your A drive, find the diskette with its boot disk virus, load it, and make it temporarily impossible to use your hard disk. (Allow several days for recovery.) This is why you should make sure you have a bootable floppy.
Macro viruses. These are among the most common viruses, and they tend to do the least damage. Macro viruses infect your Microsoft Word application and typically insert unwanted words or phrases.
The best protection against a virus is to know the origin of each program or file you load into your computer. Since this is difficult, you can buy anti-virus software that typically checks all of your files periodically and can remove any viruses that are found. From time to time, you may get an e-mail message warning of a new virus. Chances are good that the warning is a virus hoax.

VPN: A virtual private network (VPN) is a private data network that makes use of the public telecommunication infrastructure, maintaining privacy through the use of a tunnelling protocol and security procedures. A virtual private network can be contrasted with a system of owned or leased lines that can only be used by one company. The idea of the VPN is to give the company the same capabilities at much lower cost by using the shared public infrastructure rather than a private one. Phone companies have provided secure shared resources for voice messages. A virtual private network makes it possible to have the same secure sharing of public resources for data. Companies today are looking at using a private virtual network for both extranets and wide-area intranets.
Using a virtual private network involves encrypting data before sending it through the public network and decrypting it at the receiving end. An additional level of security involves encrypting not only the data but also the originating and receiving network addresses. Microsoft, 3Com, and several other companies have developed the Point-to-Point Tunneling Protocol (PPTP) and Microsoft has extended Windows NT to support it. VPN software is typically installed as part of a companys firewall server.