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Glossary U
What are the GDI heap and the USER heap? The GDI (graphical device interface) heap is one of the systemwide resources in the Windows environment. Its counterpart is the USER heap. Each is limited to 64KB and is shared by all the applications. When you launch an application in Windows, an object is placed in the USER heap. Most applications also place a GDI object in the GDI heap. If the USER heap or the GDI heap become full, your computer can crash. Theoretically, memory is reclaimed from the USER heap when you exit an application. However, this does not always occur. When you exhaust your GDI and USER heaps, you might see the outline of icons, or a partially drawn window. Perhaps some of the graphics will look like black boxes. The number of windows you can open simultaneously is also limited to the available space in the USER heap. Also see:
What are Usenet newsgroups? One of the busiest parts of the Internet, Usenet newsgroups are electronic discussion groups in which you can share information and opinions with people all over the world. You can access newsgroups with newsreaders such as trn or tin, or you can use a desktop news reader such as Netscape Navigator. Within each newsgroup, you'll find any number of articles on a given subject, and many subjects being discussed. Usenet newsgroups allow you to reply to articles you have read and to publish ("post") your own articles for others to read. Newsgroups differ widely in subject and style. Topics vary from avionics to zoology; content ranges from scientific discourse to casual chatting. With thousands of newsgroups available, there's something for just about everyone. Some groups are moderated and have regulated content, while others have a chaotic barrage of messages. Some have a very high volume of messages (hundreds or more each day), while others may have only a small trickle of articles. Newsgroups are organized and grouped by title using compound names such as rec.sport.basketball.college. Here, rec specifies recreational topics, sport specifies a subgroup of recreation, and so on. Other categories include the following:
Within each category you'll find other subgroups. If you decide to participate in a newsgroup, it's best to first read a representative selection of articles over several days or even weeks before posting. Each newsgroup may have its own set of accepted guidelines for what constitutes an appropriate posting, and becoming familiar with the group before posting will help you show good manners ("netiquette") and avoid offending others. If you are new to Usenet, you should also read the newsgroups news.newusers.questions and news.announce.newusers to learn about technique and "netiquette" before posting. You can also find a large repository of Usenet FAQ (Frequently Asked Question) files for a wide variety of newsgroups and subjects at the Usenet FAQ Files site at the following URL: It's best to read any existing FAQ for a newsgroup before posting so that you'll avoid irritating other readers by asking questions that have already been answered many times. Also see:
What is a URL? URL stands for Uniform Resource Locator, and is used to specify addresses on the World Wide Web. A URL is the fundamental network identification for any resource connected to the Web (e.g., hypertext pages, images, and sound files). URLs have the following format: protocol://hostname/other_information For example, the URL for Indiana University's home page is: The protocol specifies how information from the link is transferred. The protocol used for Web resources is HyperText Transfer Protocol (HTTP). Other protocols compatible with most Web browsers include FTP, telnet, news, and Gopher. The protocol is followed by a colon, two slashes, and then the domain name. The domain name is the computer on which the resource is located. Links to particular files or subdirectories may be further specified after the domain name. The directory names are separated by single slashes. You can find information about URLs at the World Wide Web Consortium's (W3C) Web Naming and Addressing Overview: Also see:
What is Unicode? Developed in cooperation between the Unicode Consortium and the International Organization for Standardization (ISO), Unicode is an attempt to consolidate the alphabets and ideographs of the world's languages into a single, international character set. It focuses on the characters themselves rather than on languages. Thus, a letter shared between English and Russian (or for that matter, an ideograph shared between kanji and Han script) would have the same Unicode character. As a multilingual standard, Unicode makes it possible for developers to create applications without having to resort to the costly, time-consuming task of releasing localized versions for each language. Most Western character sets are 7-bit (e.g., US ASCII) or 8-bit (e.g., Latin-1), limiting them, respectively, to 128 or 256 characters. This limitation has resulted in a slew of sets customized for each language. For languages like Chinese, Korean, and Japanese, which use heavily ideographic (i.e., based on the content of a word rather than its component sounds) writing systems consisting of thousands of characters, traditional 7- and 8-bit character sets are not adequate. Therefore, to include the character sets of the world's principal writing systems, Unicode uses primarily a 16-bit set, allowing up to 65,536 characters. This does have the consequence that Unicode text takes up twice as much disk space as text using an 8-bit character set. As a character set, Unicode does not concern itself with the specific appearance, or glyph, of a character. Instead, it includes only a code and name for each character. Individual fonts are assigned the tasks of rendering characters into glyphs, with the exact appearance of glyphs varying between fonts. Similarly, Unicode does not, for the most part, distinguish between plain and rich text, instead allowing applications to apply their own text processing and formatting. For more information about Unicode, visit the Unicode Consortium's Web page at: Also see: What is Universal Serial Bus (USB)? Universal Serial Bus (USB) is a way to connect peripheral devices to computers. It replaces the functionality of serial and parallel ports, including keyboard and mouse ports. USB uses a bus topology, which means peripherals can be daisy-chained together or connected through hubs. Up to 127 devices may be connected together at one time, and devices may be connected and disconnected while the computer is in operation (hot-swapping). To use USB peripherals, your computer must have either built-in USB capability or a USB expansion card installed. Your computer's operating system must be able to support USB as well. USB devices are self-identifying, and USB is Plug-and-Play compliant, which means that installation and configuration of USB devices will be relatively easy. It supports bandwidths as high as 12.5 megabits per second (Mbps) for standard USB, or up to 480Mbps for the upcoming USB 2.0 standard. The current USB 1.1 standard is suitable for devices which don't require very high speed data transfer rates. Other storage devices, as well as network connections, will still be connected via separate controllers to the system's expansion bus (ISA or PCI). Peripherals that use USB include digital audio devices, telephony devices, cable boxes, printers, monitors, keyboards, mice, digital cameras, and scanners. For more information about USB, including technical specifications, see: Also see:
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