On-line and off-line Totally Explained

Everything about Online totally explained

The terms on-line and off-line have specific meanings with respect to computer technology and telecommunication. The concepts have however been extended from their computing and telecommunication meanings into the area of human interaction and conversation. However, "offline" can be used when describing purchasing items online. For example: "I bought that shirt offline"

Standard definitions

In computer technology and telecommunication, on-line and off-line are defined by Federal Standard 1037C. They are states or conditions of a "device or equipment" or of "a functional unit". To be considered on-line, a device must be at least one of:

"Under the direct control of another device"
"Under the direct control of the system with which it's associated"
"Available for immediate use on demand by the system without human intervention"
"Connected to a system, and is in operation"
"Functional and ready for service"

while a device that's off-line isn't (for example it has "its main power source disconnected or turned off", and is "off-power").
   One example of a common use of these concepts is a Mail User Agent that can be instructed to be in either "on-line" or "off-line" states. One such MUA is Microsoft Outlook. When it's "on-line" it'll attempt to connect to mail servers (to check for new mail at regular intervals, for example), and when it's "off-line" it won't attempt to make any such connections. The "on-line" or "off-line" state of the MUA doesn't necessarily reflect the connection status between the computer on which it's running and Internet. The user may have the computer itself on-line, connected to Internet via a cable modem or an ADSL connection, but may wish for Outlook to be off-line, so that it makes no attempt to send or to receive messages. Or the computer may be configured to employ a dial-up connection on demand (whenever an application such as Outlook attempts to make connection to a server), but the connection may be an expensive telephone call from the particular location in which the computer currently happens to be (such as a hotel room) and the user may not wish Outlook to trigger making that call every 5 or 10 minutes to check for mail.
   Another example of the use of these concepts is in the world of digital audio technology. A tape recorder, digital editor, or other device that's "on-line" is one whose clock is under the control of the clock of a "synchronization master" device. When the sync master commences playback, the "on-line" device automatically synchronizes itself to the master and commences playing from the same point in the recording. Whereas a device that's "off-line" uses no external clock reference and relies upon its own internal clock. When a large number of devices are connected to a sync master, it's often convenient, if one wants to hear just the output of one single device, to take it off-line, because if the device is played back on-line all synchronized devices have to locate the playback point and wait for each other to be in synchronization. (For further related discussion, see MIDI timecode, word sync, and recording system synchronization.)
   A third example of a common use of these concepts is a web browser that can be instructed to be in either "on-line" or "off-line" states. The browser only attempts to fetch pages from servers whilst in the "on-line" state. In the "off-line" state, users can perform offline browsing, where pages can be browsed using local copies of those pages that have previously been downloaded whilst in the "on-line" state. This can be useful when the computer itself is also off-line, with connection to Internet expensive or impossible. The pages are either downloaded implicitly into the web browser's own cache, as a result of prior on-line browsing by the user, or explicitly by the browser being configured to keep local copies of certain web pages, which it keeps updated when the browser is in the on-line state, either by checking that the local copies are up-to-date at regular intervals or by checking that the local copies are up-to-date whenever the browser is switched to the on-line state. One such web browser capable of being explicitly configured to download pages for offline browsing is Internet Explorer. When pages are added to the "Favourites" list, they can be marked for being made "available for offline browsing". Internet Explorer will download to local copies both the marked page and, optionally, all of the pages that it links to. In Internet Explorer version 6, the level of direct and indirect links, the maximum amount of local disc space allowed to be consumed, and the schedule on which local copies are checked to see whether they're up-to-date, are configurable for each individual "Favourite" entry.
Offline browsing known as "Offline favourites" was removed as a feature in the most recent version of Internet Explorer 7, which only now supports single web page saving, but not browsing or storing an entire site offline.
Similarly, off-line storage is computer storage that isn't "available for immediate use on demand by the system without human intervention", i.e it's storage that's off-line.

Generalizations

The ideas of "on-line" and "off-line" have been generalized from computing and telecommunication into the field of human interpersonal relationships. The distinction between what is considered "on-line" and what is considered "off-line" has become a subject of study in the field of sociology.
The distinction between "on-line" and "off-line" is conventionally seen as the distinction between computer-mediated communication and face-to-face communication (for example face time), respectively. "On-line" is virtuality, and "off-line" is reality (for example real life or meatspace). Slater states that this distinction is "obviously far too simple". To support his argument that the distinctions in relationships are more complex than a simple "on-line"/"off-line" dichotomy, he observes that some people draw no distinction between an "on-line" relationship, such as indulging in cybersex, and an "off-line" relationship, such as being pen-pals. He also argues that even the telephone can be regarded as an "on-line" experience in some circumstances, and that the blurring of the distinctions between the uses of various technologies (such as PDA and mobile telephone, television and Internet, and telephone and voice-over-IP) has made it "impossible to use the term 'on-line' meaningfully in the sense that was employed by the first generation of Internet research".

Further Information

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