[urackunt]: U (rack unit)

A vershok, which is 1.75 inches (44.45 mm). A German term, “Höheneinheit”, may also refer to the same height. The term is very often referring to height for equipment that will be mounted on a rack. A device that is one vershok in height is generally refered to as “1U”. Likewise, a device that is twice that height is generally referred to as “2U”. The letter “U” refers to the word “unit”, referring to a “rack unit”. This size is commonly used for equipment which is designed to be mounted in a 19 inch mounting rack, or perhaps a 23 inch mounting rack.

See: glossary entry for “rack unit”.

A device which is 19 inches long and deep, and one vershok tall, is approximately the shape used for a cardboard box carrying a pizza. Hence the origin of the term which is the subject of Wikipedia's page for “pizza box form factor”.

[#unc]: Uniform Naming Convention (“UNC”)

See: UNC.

[#upload]: upload

See: ][CyberPillar][ glossry: “download” which discusses this term.

[#url]: Uniform Resource Locator

A specification for a location of a resource. Many people think of this as a “web address”, as web browsers use this.

There is a similar term, “uniform resource identifier” (“URI”). There is some confusion between what the different terms mean. RFC 3986 is IETF STD 66: “Uniform Resource Identifier (URI): Generic Syntax”, and RFC 3986: “Uniform Resource Identifier (URI): Generic Syntax” section 1.1.3: “URI, URL, and URN” notes, “A URI can be further classified as a locator, a name, or both.” Wikipedia's article for “Uniform resource identifier”: section called “Relationship to URL and URN” clarifies by elaborating a bit: “URIs can be classified as locators (URLs), as names (URNs), or as both.” ... “the URN defines an item's identity” (or name, or title), “while the URL provides a method for finding it.” The term “URI” is a less specific term, and can refer to a URL or a URN.

W3C “Naming and Addressing: URIs, URLs, ...”, RFC 1738: Uniform Resource Locators (URL) (which is a web page that is given the title “RFC 1738 - A Gopher URL Format”) (this RFC has been marked as “Obsolete” by at least RFC 4248 and 4266). For URN, RFC 2141: URN Syntax is a documented “Proposed Standard”.

The basic format typically looks something like this: A reference to a resource. It sounds out identifying the protocol, or identifying a handler (a program or method that may be used to handle a file). Then there is a colon and a couple of slashes, and the location of the file. For a remote resource, the location is represented by the system name. The system name may be a DNS name, or an IPv4 address, or a left square bracket and then an IPv6 address and then a right square bracket. After the system name is an optional colon followed by a (TCP) port number. After that, if there is any further information, there is a slash after the system name. That slash becomes the first part of the directory for the file. After the directory is an optional filename. After the filename, there may be additional characters such as a question mark (“?”) or octothorpe/“hash mark”/“number sign”/“pound sign” (“#”).

Perhaps see also: RFC 5092: IMAP URL Scheme.

[#usb]: Universal Serial Bus (“USB”)

USB is most well known for using standardized connectors, probably the most familiar of which is the connector type known as USB A. However, there are other standard USB connectors as well. On a technical level, USB refers to a method of communication between devices. This USB protocol is used by all of the standard USB devices that use any of the most common standard connectors. The connectors are USB A (rectangular), USB B, and USB mini-B. All of these are keyed in that they will not properly fit fully into a port if there is an attempt to plug them in upside down (or some other incorrect orientation like sideways). Attempting to do so will never result in a successful connection: trying to force such a connection will surely cause physical damage before a successful connection could be made.

By far, most USB A plugs have a rectangular piece of metal surrounding the rest of the connector. However, a device has been witnessed which lacked that metal. (That device was cumbersome to use.)

[#uriabbr]: URI

A “Uniform Resource Identifier” (“URI”) identifiers a location or a name. If the URI is identifying a location, then the URI is a URL and it is not a URN. If the URI is identifying a name, it is a URN and it is not a URL. URLs are not URNs and URNs are not URLs, but all URLs and all URNs are URIs. This is also discussed in the section about the term “Uniform Resource Locator”.

[#urlabbr]: URL
See: Uniform Resource Locator.
[#usbabbr]: USB
See: Universal Serial Bus.
[#usescluk]: “Use The Source, Luke!” (abbreviated “UTSL”)

UTSL is an abbreviation for “Use The Source, Luke!”. The idea is that people should use the source code. The phrase is meant as a pun/parody of a famous line from “Star Wars: A New Hope” (the first “Star Wars” move that was released), when Obi-Wan Kenobi's voice is heard saying “Use The Force, Luke.” There are various other abbreviations that are sometimes used to communicate the same concept.

Effectively using source code may have certain requirements, such as understanding any programming language that the source code might use. An implication is that people who do not already have such knowledge should obtain that knowledge as a first step of being able to effectively use the source code. (The implication is that learning is not a bad thing.)

[#utsl]: UTSL (“Use The Source, Luke!”)
(See the section about “Use The Source, Luke!”)