Scareware, also known as rogue security software, is software that uses false error messages to lure you into purchasing a software program. These alerts or warnings may appear on websites or within applications installed on your computer. When you click the associated download link, the software is downloaded to your computer.
A typical scareware warning message will state that your computer is infected with a virus or malware without actually scanning your computer. The message will also recommend that you download software to fix the non-existent problem. Once you download the software, the installer may install spyware, adware, or other unwanted programs on your computer. In some cases, scareware will ask you to enter personal information, similar to a phishing scam.
In order to avoid scareware schemes, it is helpful to check the source of security alerts that pop up on your computer. If the source is not known or credible, the warning message may not be legitimate. For example, if a website advertisement says your computer is infected, you can assume the message is false, since the website has no way of actually scanning the files on your computer. Installing a utility like Microsoft Security Essentials or a third-party Internet security program may also help you catch rogue security software before it can affect your computer.
While some alerts and error messages may be scareware schemes, it is important to remember that other notifications may be legitimate. For example, the alerts provided Symantec, Kaspersky, AVG and other security programs are valid and should be taken seriously. By familiarizing yourself with the security software installed on your computer, youll be able to determine which warnings are valid and which may be from scareware programs.

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 dont 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, shell most likely get the page straight from the proxy servers 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.

A petabyte is 1015 or 1,000,000,000,000,000 bytes.
One petabyte (abbreviated PB) is equal to 1,000 terabytes and precedes the exabyte unit of measurement. A petabyte is slightly less in size than a pebibyte, which contains 1,125,899,906,842,624 (250) bytes.
Since most storage devices can hold a maximum of a few terabytes, petabytes are rarely used to measure the storage capacity of a single device. Instead, petabytes are more commonly used to measure the total data stored in large computer networks or server farms. For example, Internet companies like Google and Facebook store over 100 petabytes of data on their servers.
NOTE: You can view a list of all the units of measurement used for measuring data storage.

A namespace is a group of related elements that each have a unique name or identifier. There are several different types of namespaces, and each one has a specific syntax used to define the corresponding elements. Each element within a namespace has a local name that serves as a unique identifier.
Namespaces are used in many areas of computing, such as domain names, file paths, and XML documents. Below are examples of these different applications.
The above examples are just a few types of namespaces used in computing. They are also used to define network devices and other types of computer hardware. Additionally, computer programmers often used namespaces to group related variables within the source code of a program. While there are many different types of namespaces, they all serve the same purpose — to contain a logical grouping of related elements.

The word monochrome literally means one color. Therefore, a monochrome image only includes one color, but may contain many shades. In computing, monochrome typically refers to a two-tone image, rather than one with several shades of a single color. For example, a monochrome monitor uses one color for the background and another to display text or images on the screen.
Before color monitors became standard, most computers had monochrome displays. These displays often had a black background with green text, though some displayed text in other colors, such as red or orange. While this may seem like a rudimentary way to display text, it was sufficient for typing documents, since computers still offered more text editing capabilities that a typewriter. Even after color monitors became the norm in the 1980s, monochrome displays were still used for several years as computer terminals.
Today, monochrome computer monitors are rare. By the time LCD displays replaced CRTs monitors in the early 2000s, monochrome screens had already been obsolete for several years. Now, even basic terminal displays support a wide range of colors. While you might not see monochrome monitors today, monochrome displays can still be found in other electronics, such as watches, timers, and digital clocks.
NOTE: Monochrome is not the same thing as grayscale. A grayscale image is a type of monochrome image that only contains shades of gray. Additionally, monochrome and black-and-white are two different things. The phrase black-and-white may refer to a monochrome image that only includes the colors black and white or a grayscale image with multiple shades of gray.

A metafile can refer to two different types of computer files. The first is a file that describes the contents of other files. This type of metafile may contain metadata, which defines a group other files and gives a summary of what data they contain.
The second type of metafile is most often used in computer graphics. These files define objects and images using a list of coordinates. They are typically used for vector images, such as Adobe Illustrator, CorelDRAW, and EPS files, but can include raster images as well.

A memory bank is a designated section of computer memory used for storing data. Much like financial bank, a memory bank serves as a repository for data, allowing data to be easily entered and retrieved. Banks are organized into logical units that are ordered consecutively, providing easy to access individual items.
Memory banks are commonly used for caching data. By storing frequently used information in memory banks, the data can be accessed quickly and easily. This speeds up common tasks that are run within the operating system and other programs. Various applications may also use memory banks to store data while the program is running.
Sets of physical memory modules may also be referred to as memory banks. However, to avoid confusion, these are usually called banks of memory.

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A logic error (or logical error) is a mistake in a programs source code that results in incorrect or unexpected behavior. It is a type of runtime error that may simply produce the wrong output or may cause a program to crash while running.
Many different types of programming mistakes can cause logic errors. For example, assigning a value to the wrong variable may cause a series of unexpected program errors. Multiplying two numbers instead of adding them together may also produce unwanted results. Even small typos that do not produce syntax errors may cause logic errors. In the PHP code example below, the if statement may cause a logic error since the single equal sign (=) should be a double equal sign (==).
Incorrect: if (=1) { ... }
Correct: if (==1) { ... }
In PHP, == means is equal to, while = means becomes. Therefore, the incorrect if statement always returns TRUE, since assigning 1 to the variable returns a TRUE value. In the correct code, the if statement only returns TRUE if is equal to 1. However, since the syntax of the incorrect code is acceptable, it will not produce a syntax error and the code will compile successfully. The logic error might only be noticed during runtime. Because logic errors are often hidden in the source code, they are typically harder to find and debug than syntax errors.

Stands for Java Runtime Environment and may also be written Java RTE. Java is a programming language, similar to C. However, since it is a newer language, it is not natively supported by all operating systems. Therefore, a Java Runtime Environment may need to be installed on your computer for Java applets and Java applications to run.
The JRE, or Java RTE, is developed by Sun Microsystems (the creator of Java) and includes the Java Virtual Machine (JVM), code libraries, and components, which are necessary to run programs written in Java. The JRE is available for multiple computer platforms, including Mac, Windows, and Unix.
If the JRE is not installed on a computer, Java programs may not be recognized by the operating system and will not run. The JRE software provides a runtime environment in which Java programs can be executed, just like software programs that have been fully compiled for the computers processor. JRE software is available as both a standalone environment and a Web browser plug-in, which allows Java applets to be run within a Web browser.

An IP address, or simply an IP, is a unique address that identifies a device on the Internet or a local network. It allows a system to be recognized by other systems connected via the Internet protocol. There are two primary types of IP address formats used today — IPv4 and IPv6.
There are three classes of IPv4 address sets that can be registered through the InterNIC. The smallest is Class C, which consists of 256 IP addresses (e.g. 123.123.123.xxx — where xxx is 0 to 255). The next largest is Class B, which contains 65,536 IP addresses (e.g. 123.123.xxx.xxx). The largest block is Class A, which contains 16,777,216 IP addresses (e.g. 123.xxx.xxx.xxx).
The total number of IPv4 addresses ranges from 000.000.000.000 to 255.255.255.255. Because 256 = 28, there are 28 x 4 or 4,294,967,296 possible IP addresses. While this may seem like a large number, it is no longer enough to cover all the devices connected to the Internet around the world. Therefore, many devices now use IPv6 addresses.
The IPv6 address format is much different than the IPv4 format. It contains eight sets of four hexadecimal digits and uses colons to separate each block. An example of an IPv6 address is: 2602:0445:0000:0000:a93e:5ca7:81e2:5f9d. There are 3.4 x 1038 or 340 undecillion) possible IPv6 addresses, meaning we shouldnt run out of IPv6 addresses anytime soon.
List of IP addresses from web server logs

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The personal computer market in the early 1980s consisted primarily of Apple and IBM computers. Apples systems ran a proprietary operating system developed by Apple, while IBM machines primarily ran PC-DOS. As the demand for personal computers began to grow, IBM decided to license the DOS operating system to other manufacturers. These companies began producing personal computers that were called PC clones or IBM compatibles.
As several other manufacturers began producing PCs, supplies grew and costs began to drop. This enabled more people to afford PCs and sales of IBM compatibles began to dominate the personal computer market. It wasnt long until the new manufacturers PC sales surpassed the number of computers sold directly by IBM. The Apple Macintosh also gained substantial market share when it was introduced in 1984, but the low cost and wide availability of IBM compatibles kept their sales strong.
Sales of IBM compatibles surged again in 1995, when Microsoft introduced the Windows 95 operating system. However, by that time, the term IBM compatible had become almost irrelevant, since most PCs used Microsoft Windows as the primary operating system. Also, PC manufacturers had been building their own computers for many years, and there were few similarities between IBMs own PCs and IBM compatibles.
In 2005, IBM stopped manufacturing personal computers. The company that started the PC revolution is no longer in the market. Therefore, the term IBM compatible is a bit outdated, though it can still be used to describe Windows-based computers. The term PC is more appropriate, albeit a bit ambiguous, since Macs are technically PCs too. Therefore, the term Windows computer seems to be the best way to describe a modern day IBM compatible.

Grayscale is a range of monochromatic shades from black to white. Therefore, a grayscale image contains only shades of gray and no color.
While digital images can be saved as grayscale (or black and white) images, even color images contain grayscale information. This is because each pixel has a luminance value, regardless of its color. Luminance can also be described as brightness or intensity, which can be measured on a scale from black (zero intensity) to white (full intensity). Most image file formats support a minimum of 8-bit grayscale, which provides 2^8 or 256 levels of luminance per pixel. Some formats support 16-bit grayscale, which provides 2^16 or 65,536 levels of luminance.
Many image editing programs allow you to convert a color image to black and white, or grayscale. This process removes all color information, leaving only the luminance of each pixel. Since digital images are displayed using a combination of red, green, and blue (RGB) colors, each pixel has three separate luminance values. Therefore, these three values must be combined into a single value when removing color from an image. There are several ways to do this. One option is to average all luminance values for each pixel. Another method involves keeping only the luminance values from the red, green, or blue channel. Some programs provide other custom grayscale conversion algorithms that allow you to generate a black and white image with the appearance you prefer.
While grayscale is an important aspect of digital images, it also applies to printed documents. When you select Print, the print dialog box that appears may include a grayscale option. If you choose this option, the color information will be removed from the document before it is printed. As long as your printer has an individual black ink cartridge, when you print in grayscale, it should only use the black ink and none of the color cartridges. Therefore, the Print in Grayscale feature is useful if you just need to print a document for reference or dont need a color version.

Stands for Floating Point Operations Per Second. FLOPS are typically used to measure the performance of a computers processor. While clock speed, which is measured in megahertz, is often seen as an indicator or a processors speed, it does not define how many calculations a processor can perform per second. Therefore, FLOPS is a more raw method of measuring a processors processing speed.
Still, a FLOPS reading only measures floating point calculations and not integer operations. Therefore, while FLOPS can accurately measure a processors floating point unit (FPU), it is not a comprehensive measurement of a processors performance. In order to accurately gauge the processing capabilities of a CPU, multiple types of tests must be run.

In the computer world, flexible may refer to hardware, software, or a combination of the two. It describes a device or program that can be used for multiple purposes, rather than a single function.
An example of a flexible hardware device is a hybrid tablet that also functions as a laptop. The Microsoft Surface, for instance, is more flexible than typical tablet, since it can also be used as a Windows laptop. A router that can serve as a firewall for both internal and external networks might also be considered flexible. Instead of being limited to filtering traffic from the Internet, a flexible router may be used to filter traffic within a local network as well.
Horizontal market software, which is used across multiple industries, is a common type of flexible software. Spreadsheet programs, for example, are flexible because they provide a range of uses, such as managing team rosters, tracking inventory, and organizing finances. A professional design program like Adobe InDesign may be considered flexible, since it can be used to create digital layouts for print, web, and electronic publications. Web browser are flexible since they serve many different purposes. Besides surfing the web, you can use a browser to check email, interact with social media sites, play games, and run various web applications.
Flexible hardware and software products provide extra value since they can be used in many different ways. However, flexibility is not always important. In some cases, a device or program designed for a specific purpose can perform a task better than a multipurpose solution.

Stands for First In, Last Out. FILO is an acronym used in computer science to describe the order in which objects are accessed. It is synonymous with LIFO (which is more commonly used) and may also be called LCFS or last come, first served.
A stack is a typical data structure that may be accessed using the LIFO method. In a stack, each item is placed on top of the previous item, one at a time. Items can be removed from either the top of the stack (FILO) or from the bottom of the stack FIFO. You can imagine a FILO stack as the paper in a printer tray. Whatever paper you place on top of the existing paper in the input tray will be accessed first.
FILO is not necessarily a fair way to access data, since it operates in opposite order of a queue. Still, the FILO method can be useful for retrieving recently used objects, such as those stored in cache memory.

A filename is a text string that identifies a file. Every file stored on a computers hard disk has a filename that helps identify the file within a given folder. Therefore, each file within a specific folder must have a different filename, while files in different folders can have the same name.
Filenames may contain letters, numbers, and other characters. Depending on the operating system, certain characters cannot be used since they conflict with operators or other syntax used by the operating system. Different operating systems also have different limits for the number of characters a filename can have. While older operating systems limited filenames to only 8 or 16 characters, newer OSs allow filenames to be as long as 256 characters. Of course, for most practical purposes, 16 characters is usually enough.
Filenames also usually include a file extension, which identifies the type of file. The file extension is also called the filename suffix since it is appended to the filename, following a dot or period. For example, a Microsoft Word document may be named document1.doc. While technically the filename in the preceding example is document1 and doc is the extension, it is also acceptable to refer to document1.doc as the filename. In some cases, the filename may even refer to the files directory location, i.e. (\My Documents\School Papers\document1.doc).
You can name a file by clicking on the files icon or filename, waiting for a second, then clicking on the filename again. As long as the file is not locked, the filename will become highlighted, and you can type a new name for the file. You can also name a file the first time you save it from a program or by selecting Save As... from the programs File menu.

File compression is used to reduce the file size of one or more files. When a file or a group of files is compressed, the resulting archive often takes up 50% to 90% less disk space than the original file(s). Common types of file compression include Zip, Gzip, RAR, StuffIt, and 7z compression. Each one of these compression methods uses a unique algorithm to compress the data.
So how does a file compression utility actually compress data? While each compression algorithm is different, they all work in a similar fashion. The goal is to remove redundant data in each file by replacing common patterns with smaller variables. For example, words in a plain text document might get replaced with numbers or another type of short identifier. These identifiers then reference the original words that are saved in a key within the compressed file. For instance, the word computer may be replaced with the number 5, which takes up much less space than the word computer. The more times the word computer is found in the text document, the more effective the compression will be.
While file compression works well with text files, binary files can also be compressed. By locating repeated binary patterns, a compression algorithm can significantly reduce the size of binary files, such as applications and disk images. However, once a file is compressed, it must be decompressed in order to be used. Therefore, if you download or receive a compressed file, you will need to use a file decompression program, such as WinZip or StuffIt Expander, to decompress the file before you can view the original contents.
Related file extensions: .ZIP, .GZ, .RAR, .SITX, .7Z.

Extensible is an IT term used to describe something that can be extended or expanded from its initial state. It typically refers to software, such as a program or file format, though it can also be used to describe a programming language itself.
An extensible software program, for example, might support add-ons or plug-ins that add extra functionality to the program. It may also allow you to add custom functions or macros that perform specialized tasks within the application. An extensible file format (like XML) can be customized with user-defined elements.
If a programming language is extensible, it may support custom syntax and operations. These custom elements can be defined in the source code and are recognized by the compiler along with the pre-defined elements. Examples of extensible programming languages include Ruby, Lua, and XL.
While the terms scalable and extensible are sometimes used interchangeably, they are not the same thing. Scalability can refer to hardware, software, or an entire IT system, such as a cloud-based service. Extensibility, on the other hand, is almost always used to describe software and refers specifically to its extendable capabilities. For instance, a software program that supports plugins is extensible, but not necessarily scalable. A server rack that has several empty slots for future use may be considered scalable, but is not extensible.