What is P2P?
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Stands for "Peer to Peer." In a P2P network, the "peers" are computer systems which are connected to each other via the Internet. Files can be shared directly between systems on the network without the need of a central server. In other words, each computer on a P2P network becomes a file server as well as a client.
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What is Packet?
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This is a small amount of computer data sent over a network. Any time you receive data from the Internet, it comes to your computer in the form of many little packets. Each packet contains the address of its origin and destination, and information that connects it to the related packets being sent. The process of sending and receiving packets is known as "packet-switching." Packets from many different locations can be sent on the same lines and be sorted and directed to different routes by various computers along the way. It works a lot like the post office, except billions of packets are transferred each day, and most packets take less than a few seconds to reach their destination. Even FedEx same-day delivery can't compete with that.
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What is PageRank?
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PageRank is a family of algorithms for assigning numerical weightings to hyperlinked documents (or web pages) indexed by a search engine. Its properties are much discussed by search engine optimization (SEO) experts. The PageRank system is used by the popular search engine Google to help determine a page's relevance or importance. It was developed by Google's founders Larry Page and Sergey Brin while at Stanford University in 1998. As Google puts it.
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What is Parallel Port?
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This interface is found on the back of older PCs and is used for connecting external devices such as printers or a scanners. It uses a 25-pin connector (DB-25) and is rather large compared to most new interfaces. The parallel port is sometimes called a Centronics interface, since Centronics was the company that designed the original parallel port standard. It is sometimes also referred to as a printer port because the printer is the device most commonly attached to the parallel port. The latest parallel port standard, which supports the same connectors as the Centronics interface, is called the Enhanced Parallel Port (EPP). This standard supports bi-directional communication and can transfer data up to ten times faster than the original Centronics port. However, since the parallel port is a rather dated technology, don't be surprised to see USB or Firewire interfaces completely replace parallel ports in the future.
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What is Parse?
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To break down a string of information such as a command or file into its constituent parts.
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What is Partition?
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A partition is a section of a hard disk. When you format a hard disk, you can usually choose the number of partitions you want. The computer will recognize each partition as a separate disk, and each will show up under "My Computer" (Windows) or on the desktop (Macintosh).
So why would you want to create multiple partitions? Well, there are two main reasons. One is if you want to have multiple operating systems on your computer. Typically, an operating system needs to be installed on its own partition so that it won't conflict with other operating systems on the machine. The other reason is that multiple partitions can improve the efficiency of your hard disk. On larger disks, the cluster or block size (which is the minimum amount of space a file can take up), is larger than on small disks. This can result in a waste of disk space if you have a lot of small files. So creating multiple partitions can actually give you more space. Yep, more room for all those MP3s. "Partition" can also be used as a verb, meaning to create multiple partitions.
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What is Password?
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A password is a string of characters used for authenticating a user on a computer system. For example, you may have an account on your computer that requires you to log in. In order to successfully access your account, you must provide a valid username and password. This combination is often referred to as a login. While usernames are generally public information, passwords are private to each user.
Most passwords are comprised of several characters, which can typically include letters, numbers, and most symbols, but not spaces. While it is good to choose a password that is easy to remember, you should not make it so simple that others can guess it. The most secure passwords use a combination of letters and numbers and don not contain actual words.
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What is Paste?
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Just like you can paste a note on a sheet of paper, you can paste data into a document on a computer. The paste function can be used to paste copied data into text documents, images, Web browser address fields, and just about any place where you can enter data. However, to paste data, you first need to copy it to the "Clipboard," which is a temporary storage area in your system's memory, or RAM. This is done by first selecting the data you want to copy and then choosing "Copy" from the program's Edit menu.
Once you have data copied to the Clipboard, you can paste it within the same document or within a different document in the same program. You can even paste copied data into a document within a different program. However, you can typically only paste data into a document with the same kind of data. For example, you cannot paste an image into your Web browser's address field or an audio file into image editing program.
To paste a copied piece of data, select "Paste" from the Edit menu in the program you wish to paste the data in. Text documents or programs with text fields will typically paste the data wherever the flashing cursor is. You can also use the keyboard shortcut "Control-V" for Windows or "Command-V" for the Mac OS to paste the data. The reason the "V" key is used is because the "P" key is usually reserved for the "Print" shortcut and "V" is right next to the "C" key, which is used for copying. So it might not be that intuitive at first, but it makes sense when you think about it. =)
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What is Payload?
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When data is sent over the Internet, each unit transmitted includes both header information and the actual data being sent. The header identifies the source and destination of the packet, while the actual data is referred to as the payload. Because header information, or overhead data, is only used in the transmission process, it is stripped from the packet when it reaches its destination. Therefore, the payload is the only data received by the destination system.
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What is PCB?
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Stands for "Printed Circuit Board." A PCB is a thin board made of fiberglass or a similar material. Electrical wires are "printed" onto the board, connecting the microprocessor to other components on the board. Some examples of PCBs include motherboards, RAM chips, and network interface cards.
Printed circuit boards are sometimes abbreviated as "PC boards," which is fitting, since the boards are commonly used in personal computers. However, PCBs are also found in other types of electronic devices, such as radios, televisions, and computer monitors. Because PCBs are relatively flat, they can also be used in thin devices such as laptops and portable music players.
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What is PCI?
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Stands for "Peripheral Component Interconnect." It is a hardware bus designed by Intel and used in both PCs and Macs. Most add-on cards such as SCSI, Firewire, and USB controllers, use a PCI connection. Some graphics cards use PCI, but most new graphics cards connect to the AGP slot. PCI slots are found in the back of your computer and are about 3.5" long and about 0.5" high. So before you go buy that Firewire expansion card, make sure you have at least one PCI slot available.
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What is PCMCIA?
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Stands for "Personal Computer Memory Card International Association." It can also mean, perhaps more appropriately, "People Can't Memorize Computer Industry Acronyms." This way-to-long acronym stands for an association founded in 1989 which develops standards for expansion cards for portable computers. However, the term is most commonly associated with the actual cards standardized by the organization. These cards are referred to as "PCMCIA cards," or simply "PC cards." There are three types of PCMCIA cards, all of which are rectangular and measure 8.56 by 5.4 cm., but have different widths:
Type I: up to 3.3 mm. thick, mainly used to add additional ROM or RAM.
Type II: up to 5.5 mm. thick, typically used for fax/modem cards.
Type III: up to 10.5 mm. thick, often used to attach portable disk drives.
PCMCIA slots also come in three sizes -- a Type I slot can hold one Type I card, a Type II slot can hold one Type II card or two Type I cards, and a Type III slot can hold one Type III card or one Type I and one Type II card. PC Cards can be removed or inserted "on the fly," which means you don't have to turn your computer off to exchange them and you don't have to restart for your computer to recognize them.
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What is PDA?
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Stands for "Personal Digital Assistant." These are the little electronic devices you see people jotting stuff down on in public. Usually, when you see someone with a PDA, they will be holding it out far front of them for everyone to see. Fortunately, as PDAs become more common, more people will have them and we won't have to deal with the people who make sure everyone else sees that they have one.
The first PDA, called the Newton, was created by Apple in 1993. Since then, numerous other companies have jumped on the bandwagon and have added many new designs and options to the PDA market. The Palm Pilot, Handspring Visor, HP Jordana, Compaq Aero, Sharp Mobilon, and Sony Clié are all common PDAs. Ironically, Apple's Newton was discontinued when the company was having financial difficulties in 1998. Today's PDAs allow you to organize your schedule, take notes, do math calculations, play games, write memos, and even surf the Internet and send e-mail. They are cool things to have, but if you decide to get one, please do us all a favor and don't show it off in public.
PDA also stands for "Public Display of Affection," and though this term is all too relevant at college campuses, it has nothing to do with this definition.
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What is PDF?
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Stands for "Portable Document Format." PDF is a multi-platform file format developed by Adobe Systems. A PDF file captures document text, fonts, images, and even formatting of documents from a variety of applications. You can e-mail a PDF document to your friend and it will look the same way on his screen as it looks on yours, even if he has a Mac and you have a PC. Since PDFs contain color-accurate information, they should also print the same way they look on your screen.
To view a PDF file, you need Adobe Reader, a free application program distributed by Adobe Systems. Adobe also makes an Acrobat Plug-in for Web browsers that enables PDF files to be viewed inside a browser window. For more information on PDFs, visit Abobe's PDF Page.
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What is Pebibyte?
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A pebibyte is a unit of data storage that equals 2 to the 50th power, or 1,125,899,906,842,624 bytes.
While a petabyte can be estimated as 10^15 or 1,000,000,000,000,000 bytes, a pebibyte is exactly 1,125,899,906,842,624 bytes. This is to avoid the ambiguity associated with the size of petabytes. A pebibyte is 1,024 tebibytes and precedes the exbibyte unit of measurement.
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What is Peripheral?
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A computer peripheral is any external device that provides input and output for the computer. For example, a keyboard and mouse are input peripherals, while a monitor and printer are output peripherals. Computer peripherals, or peripheral devices, are sometimes called "I/O devices" because they provide input and output for the computer. Some peripherals, such as external hard drives, provide both input and output for the computer.
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What is Perl?
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Perl, also Practical Extraction and Report Language, is a programming language released by Larry Wall on December 18, 1987 that borrows features from C, sed, awk, shell scripting and from many other programming languages.
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What is Permalink?
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Short for "permanent link." A permalink is a URL that links to a specific news story or Web posting. Permalinks are most commonly used for blogs, which are frequently changed and updated. They give a specific Web address to each posting, allowing blog entries to be bookmarked by visitors or linked to from other websites.
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What is Petabyte?
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A petabyte is 2 to the 50th power, or 1,125,899,906,842,624 bytes.
It can be estimated as 10 to the 15th power, or 1,000,000,000,000,000 bytes. A petabyte is 1,024 terabytes and precedes the exabyte unit of measurement. Since even the largest hard drives are measured in terabytes, petabytes are only used to measure the storage space of multiple hard drives or other collections of data. And no, "petabyte" is not what you do to make a byte purr.
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What is Pharming?
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Pharming is yet another way hackers attempt to manipulate users on the Internet. While phishing attempts to capture personal information by getting users to visit a fake website, pharming redirects users to false websites without them even knowing it.
While a typical website uses a domain name for its address, its actual location is determined by an IP address. When a user types a domain name into his or her Web browser's address field and hits enter, the domain name is translated into an IP address via a DNS server. The Web browser then connects to the server at this IP address and loads the Web page data. After a user visits a certain website, the DNS entry for that site is often stored on the user's computer in a DNS cache. This way, the computer does not have to keep accessing a DNS server whenever the user visits the website.
One way that pharming takes place is via an e-mail virus that "poisons" a user's local DNS cache. It does this by modifying the DNS entries, or host files. For example, instead of having the IP address 17.254.3.183 direct to www.apple.com, it may direct to another website determined by the hacker. Pharmers can also poison entire DNS servers, which means any user that uses the affected DNS server will be redirected to the wrong website. Fortunately, most DNS servers have security features to protect them against such attacks. Still, they are not necessarily immune, since hackers continue to find ways to gain access to them.
While pharming is not as common as phishing scams are, it can affect many more people at once. This is especially true if a large DNS server is modified. So, if you visit a certain website and it appears to be significantly different than what you expected, you may be the victim of pharming. Restart your computer to reset your DNS entries, run an antivirus program, then try connecting to the website again. If the website still looks strange, contact your ISP and let them know their DNS server may have been pharm
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What is Phishing?
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Phishing is similar to fishing in a lake, but instead of trying to capture fish, phishers attempt to steal your personal information. They send out e-mails that appear to come from legitimate websites such as eBay, PayPal, or other banking institutions. The e-mails state that your information needs to be updated or validated and ask that you enter your username and password, after clicking a link included in the e-mail. Some e-mails will ask that you enter even more information, such as your full name, address, phone number, social security number, and credit card number. However, even if you visit the false website and just enter your username and password, the phisher may be able to gain access to more information by just logging in to you account.
Phishing is a con game that scammers use to collect personal information from unsuspecting users. The false e-mails often look surprisingly legitimate, and even the Web pages where you are asked to enter your information may look real. However, the URL in the address field can tell you if the page you have been directed to is valid or not. For example, if you are visiting an Web page on eBay, the last part of the domain name should end with "ebay.com." Therefore, "http://www.ebay.com" and "http://cgi3.ebay.com" are valid Web addresses, but "http://www.ebay.validate-info.com" and "http://ebay.login123.com" are false addresses, which may be used by phishers. If URL contains an IP address, such as 12.30.229.107, instead of a domain name, you can almost be sure someone is trying to phish for your personal information.
If you receive an e-mail that asks that you update your information and you think it might be valid, go to the website by typing the URL in your browser's address field instead of clicking the link in the e-mail. For example, go to "https://www.paypal.com" instead of clicking the link in an e-mail that appears to come from PayPal. If you are prompted to update your information after you have manually typ
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What is PHP?
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PHP is a widely-used open-source programming language primarily for server-side applications and developing dynamic web content.
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What is PIM?
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Stands for "Personal Information Manager." A PIM is a software application that serves as a planner, notebook, and address book all in one. It can also include things like a calculator, clock , and photo album. PIMs are especially popular for PDAs (Personal Digital Assistants), since this is why most people have them. However, for those of us who don't have all the latest portable gadgets, PIM programs are also developed for desktop computers.
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What is Ping?
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This term refers to a golf equipment brand, as well as the sound made by striking your glass with a spoon at the dinner table. However, it also has a computer-related meaning. A ping is a test to see if a system on the Internet is working. "Pinging" a server tests and records the response time of the server. Pinging multiple computers can be helpful in finding Internet bottlenecks, so that data transfer paths can be rerouted a more efficient way. A good way to make sure you do not get disconnected from your dial-up ISP for being idle is to send a ping every 5 minutes or so. There are a number of shareware Ping programs that will do this for you.
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What is Pipeline?
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Computer processors can handle millions of instructions each second. Once one instruction is processed, the next one in line is processed, and so on. A pipeline allows multiple instructions to be processed at the same time. While one stage of an instruction is being processed, other instructions may be undergoing processing at a different stage. Without a pipeline, each instruction would have to wait for the previous one to finish before it could even be accessed.
To understand the benefit of a pipeline, imagine that a car manufacturing plant had to wait for each car to be fully completed before starting on the next one. That would be horribly inefficient, right? It makes much more sense to work on many cars at once, completing them one stage at a time. This is what a pipeline in a computer allows. Pipelining, as it is called, often keeps around six instructions at once in the processor at different stages of processing. Pipelines can be used for the CPU as well as for accessing memory (DRAM).
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What is Pixel?
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The term "pixel" is actually short for "Picture Element." These small little dots are what make up the images on computer displays, whether they are flat-screen (LCD) or tube (CRT) monitors. The screen is divided up into a matrix of thousands or even millions of pixels. Typically, you cannot see the individual pixels, because they are so small. This is a good thing, because most people prefer to look at smooth, clear images rather than blocky, "pixelated" ones. However, if you set your monitor to a low resolution, such as 640x480 and look closely at your screen, you will may be able to see the individual pixels. As you may have guessed, a resolution of 640x480 is comprised of a matrix of 640 by 480 pixels, or 307,200 in all. That's a lot of little dots.
Each pixel can only be one color at a time. However, since they are so small, pixels often blend together to form various shades and blends of colors. The number of colors each pixel can be is determined by the number of bits used to represent it. For example, 8-bit color allows for 2 to the 8th, or 256 colors to be displayed. At this color depth, you may be able to see "graininess," or spotted colors when one color blends to another. However, at 16, 24, and 32-bit color depths, the color blending is smooth and, unless you have some kind of extra-sensory vision capability, you should not see any graininess.
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What is Plain Text?
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Text documents come in to flavors - "rich text" and "plain text." Plain text, as you might have guessed, is rather plain. While it supports standard ASCII characters, including numbers, symbols, and spaces, it does not support any type of text formatting. Therefore you cannot use bold, italics, underlining, or different font sizes in a plain text document.
Because plain text does not contain information about text sizes or styles, it is the most efficient way to store text. Plain text documents often take up less than half the size of rich text documents containing the same number of characters.
You can use a basic text editor such as Windows Notepad to create a plain text document. If you want to copy text from a formatted document without copying the style, you can also use Notepad. Just copy the text from the original document, paste it into Notepad, then copy it again. The unformatted text will be copied from Notepad to your clipboard. The next time you paste the text, it will be pasted as plain text.
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What is Platform?
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In the computer world, a "platform" typically refers to a computer's operating system. For example, a Dell computer running Windows XP would be considered to be running on a Windows platform. An iMac, on the other hand, runs on the Macintosh platform. It is a more generic way of referring to a computer's operating system than having to specify, for example, Windows XP Professional SP 2, or Mac OS X 10.3.5. The term platform is often used when referring to what kind of computer systems a certain software program will run on.
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What is Plug-in?
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Though software plug-ins might not make your room smell as nice as the scented ones you stick in an outlet, they are still useful. A software plug-in is an add-on for a program that adds functionality to it. For example, a Photoshop plug-in (such as Eye Candy) may add extra filters that you can use to manipulate images. A browser plug-in (such as Macromedia Flash or Apple QuickTime) allows you to play certain multimedia files within your Web browser. VST plug-ins add effects for audio recording and sequencing programs such as Cubase and Logic Audio.
Most graphics and audio programs today support plug-ins since they are a convenient way to expand the capabilities of the program. Though some plug-ins may be shipped with the program, most are developed by third-parties and are sold separately. Because companies that make browser plug-ins are often competing for a standard (such as Flash and QuickTime), these plug-ins are usually available as free downloads from the Internet.
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What is PNG?
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Stands for "Portable Network Graphic." This format was designed as an alternative to the GIF format (which has been plagued by copyright issues). Like GIFs, PNG files are lossless, meaning they don't lose any detail when they are compressed. They support up to 48-bit color or 16-bit grayscale and typically compress about 5% to 25% better than GIF files. However, they do not support animations like GIFs do. A format similar to PNG, called MNG, is currently under development, and will support animations.
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What is POP3?
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Post Office Protocol version 3 (POP3) is an application layer Internet standard protocol used to retrieve email from a remote server to a local client over a TCP/IP connection. Nearly all individual Internet service provider email accounts are accessed via POP3
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What is Popunder?
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Pop-under ads are a form of online advertising that, spawns a new browser window in the background.
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What is Popup?
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Pop-up ads are a form of online advertising on the World Wide Web intended to increase web traffic. It works when certain web sites open a new web browser window to display advertisements. The pop-up window containing an advertisement is usually generated by JavaScript, but can be generated by other means as well. A less intrusive variation on the pop-up window is the pop-under advertisement. This opens a new browser window, but in the background, so as not to interrupt the user's page-view.
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What is Port?
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As if computer terms weren't hard enough to understand, there are three different meanings of the word "port."
1. An Internet port. This is a number that indicates what kind of protocol a server on the Internet is using. For example, Web servers typically are listed on port 80. Web browsers use this port by default when accessing Web pages, but you can also specify what port you would like to use in the URL like this: http://www.excite.com:80. FTP uses port 21, e-mail uses port 25, and game servers, like a Quake server or Blizzard.net use various other ports. It is good to know what a port is, but you seldom have to specify it manually, so don't worry if this is new to you.
2. A hardware port. This refers to any one of the ports that are on the back of a computer where devices can be hooked up (like a keyboard, mouse, printer, digital camera, etc). Some common ports found on today's computers are USB, Firewire, and Ethernet.
3. The verb, "port." This refers to the editing of a software program's code so that it can run on another platform. For example, to get Final Fantasy VII to run on a PC, programmers needed to port it to the PC from the Playstation. Popular Windows games are often ported to the Macintosh as well.
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What is Portal?
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A portal is a web site that provides a starting point, a gateway, or portal, to other resources on the Internet or an intranet. Intranet portals are also known as "enterprise information portals" (EIP).
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What is PostScript?
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PostScript is a page description language (PDL) that describes a page's text and graphical content. It can be used to define the appearance of graphics and text for both screen and print. The language was developed by Adobe in 1984 and has since gone through may revisions and updates.
Before PostScript was introduced, publishing systems relied on proprietary typesetting systems, which often caused incompatibilities between computers and printing systems. In fact, before the days of PostScript, pages that incorporated text, images, and line art had to be manually assembled on a paste-up board and then photographed. The resulting picture was sent to a printing plate, which was used to make copies of the document -- pretty archaic compared to the simple printing options available today.
Adobe PostScript makes it possible to produce high quality page content that can include text, images, and line art in a standard format compatible with multiple devices. For example, PostScript (.PS) files will print the exact same way from different PostScript compatible printers. They can also be opened using Adobe Acrobat and will look the same on Macintosh and Windows platforms. In fact, the evolution of PostScript led to the development of Adobe Acrobat, which creates PDF documents.
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What is Power User?
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When it comes to computers, there are regular users and there are power users. Most people fall into the regular computer user category. These types of people use their computers for basic functions like Web browsing, sending e-mails, typing papers, working with spreadsheets, doing finances, and playing games. Regular computer users can typically get by with a middle-of-the-line computer that is fast enough to do their everyday work.
Power users, however, require top-of-the-line machines that are optimized for their work purposes. Power users include video-editing professionals, high-end graphic designers, audio producers, and those who use their computers for scientific research. Professional gamers (yes, there is such a thing) also fall under this category. These users seek the latest and greatest systems because no computer is really "fast enough" to suit their needs. Even the fastest computers can take substantial time to render large amounts of video and audio or to manipulate large images. Gamers want machines that will play their games in as many frames per second (FPS) as possible. So, to be a power user means to never be really satisfied with your system, but to always want something faster and better. Then again, that sounds like most of us, but power users usally have justifiable reasons.
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What is PPC?
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Pay per click, or PPC, is an advertising technique used on websites, especially search engines. Pay per click advertisements are usually text ads placed near search results; when a site visitor clicks on the advertisement, the advertiser is charged a small amount. Variants include pay for placement and pay for ranking. Pay per click is also sometimes known as Cost per click or CPC.
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What is PPGA?
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Stands for "Plastic Pin Grid Array" (not the Pretty People Golfer's Association). PPGA is a type of processor design or "form factor" used by the Intel Celeron processor. The design allows the heat generated by the chip to dissipate more quickly. This enables the processor to use more transistors and run at higher speeds without burning a hole in the side of your computer.
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What is PPL?
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Pay per lead, or PPL, is an ad pricing structure by which the advertiser pays the publisher according to how many leads are generated by an ad, often determined by information submitted directly into the banner ad.
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What is PPP?
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Stands for "Point to Point Protocol." It is the Internet standard for dial-up modem connections. PPP is a set of rules that defines how your modem exchanges packets of data with other systems on the Internet. If you connect to your ISP with a dial-up modem, you are most likely using PPP.
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What is PRAM?
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Stands for "Parameter Random Access Memory," and is pronounced "P-ram." PRAM is a type of memory found in Macintosh computers that stores system settings. These settings include display settings (like screen resolution and color depth), the time zone setting, speaker volume, and the startup volume choice. The system settings that are stored in the computer's PRAM differ from Mac to Mac, but the purpose of the memory remains the same.
If your Macintosh is behaving erratically or is not booting up all the way, you may want to try resetting the PRAM. You can reset or "zap" the PRAM on a Mac by pressing and holding the Command, Option, P, and R keys right as you turn the computer on. Yes, there are four keys you need to hold down at the same time. Once your hear the startup chime a second time, the PRAM has been reset and you can release the keys.
Note that if you choose to zap your PRAM, you may need to set your display, time zone, startup volume, and other affected settings using System Preferences. Some firmware updates may reset your PRAM as part of their installation process, which will means you will have to reset the affected settings after the installation.
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What is Process?
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A process is a program that is running on your computer. This can be anything from a small background task, such as a spell-checker or system events handler to a full-blown application like Internet Explorer or Microsoft Word. All processes are composed of one or more threads.
Since most operating systems have many background tasks running, your computer is likely to have many more processes running than actual programs. For example, you may only have three programs running, but there may be twenty active processes. You can view active processes in Windows by opening the Task Manager (press Ctrl-Alt-Delete and click Task Manager). On a Mac, you can see active processes by opening Activity Monitor (in the Applications->Utilities folder).
The term "process" can also be used as a verb, which means to perform a series of operations on a set of data. For example, your computer's CPU processes information sent to it by various programs.
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What is Progressive Scan?
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Video signals are generated using horizontal lines. An interlaced picture draws every other line and alternates between drawing odd lines and even lines. A progressive scan picture draws every line in sequence. Therefore, a progressive scan video signal sends twice as much data than an interlaced signal each time it draws an image on the screen.
Before DVDs and HDTV became popular, interlaced video was the norm for television. Standard definition broadcasts were interlaced, since it was a more efficient way to send video data. Since the human eye has a hard time detecting video interlacing, an interlaced signal that refreshes at 60 Hz (times per second) is easier on the eyes and produces less flicker than a progressive scan signal that refreshes at 30 Hz.
Still, if a progressive scan and interlaced image are both projected at 60 Hz, the progressive scan image will usually appear slightly smoother. Video that contains fast motion makes this difference more noticeable. For this reason, the DVD and HDTV standards were developed to support progressive scan video signals.
When you see video formats described as 480p or 720p, the number indicates how many horizontal lines of resolution the video signal uses, while the "p" indicates it is a progressive scan signal. Similarly, the 1080i format contains 1080 lines of resolution, but is interlaced. Both 720p and 1080i are used by HDTV.
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What is Protocol?
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When computers communicate with each other, there needs to be a common set of rules and instructions that each computer follows. A specific set of communication rules is called a protocol. Because of the many ways computers can communicate with each other, there are many different protocols -- too many for the average person to remember. Some examples of these different protocols include PPP, TCP/IP, SLIP, HTTP, and FTP. Can you guess what the last "P" in each acronym stands for? If you guessed "protocol," send yourself a congratulations e-mail.
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What is Proxy Server?
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Most large businesses, organizations, and universities these days use a proxy server. This is a server that all computers on the local network have to go through before accessing information on the Internet. By using a proxy server, an organization can improve the network performance and filter what users connected to the network can access.
A proxy server improves Internet access speeds from a network primarily by using a caching system. Caching saves recently viewed Web sites, images, and files on a local hard drive so that they don't have to be downloaded from the Web again. While your Web browser might save recently viewed items on your computer, a proxy server caches everything accessed from the network. That means if Bob views a news story at cnn.com at 1:00 and Jill views the same page at 1:03, she'll most likely get the page straight from the proxy server's cache. Though this means super-fast access to Web pages, it also means users might not be seeing the latest update of each Web page.
The other main purpose a proxy server is to filter what is allowed into the network. While HTTP, FTP, and Secure protocols can all be filtered by a proxy server, HTTP is the most common. The proxy server can limit what Web sites users on the network can access. Many organizations choose to block access to sites with objectionable material such as hacking information and pornography, but other sites can be filtered as well. If an employer notices workers are spending too much time at sites like eBay or Quicken.com, those sites can be blocked by the proxy server as well.
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What is PSA?
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A public service announcement or PSA is a non-commercial "advertisement" for web sites.
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