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Asked: 2026-06-06T10:45:23+00:00

Wikipedia states that underscores are used by both Android and Microsoft Windows Systems in

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Wikipedia states that underscores are used by both Android and Microsoft Windows Systems in hostnames. My question is, what are these host names? Do you have examples of these strange hostnames names and what they are used for?

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  1. Editorial Team

    What are host names?

    Analogous to a school class room where each student has a roll number/id so that he/she is identified, in the class room of Internet (or for that matter any computer network) each device that are in the network needs to be uniquely identified. This is done via a Host Name. Thus hostnames are names that helps in identifying devices in a network.

    Hostnames with underscore(_) character.

    During the period when the standards were being laid for the valid and invalid hostnames, the common terminal interface was the keyboard of the Teletype (TTY) ASR-33. Now this keyborad never had a underscore(_) key in it (check this pic http://www.pdp8.net/asr33/pics/kbd_top.shtml?large) and hence it was not possible to have a hostname with an underscore(_) in it. Check this link for more details: http://www.quora.com/Domain-Name-System-DNS/Why-are-underscores-not-allowed-in-DNS-host-names

    Underscore(_) character can be used in the domain names. As this post states Can (domain name) subdomains have an underscore "_" in it? it is completely valid to have an underscore. Some examples(as shown in the post) are _jabber._tcp.gmail.com or _sip._udp.apnic.net. Another example of usage of an underscore is seen here http://ideaharbor.org/notes/technical/enabling-chat-outside-google-apps. Though its valid to use underscores it not a recommended practice.

    The wikipedia link in your post states that Microsoft Windows and Android smartphones does not enforce the rule against using an underscore in hostnames. Non enforcement of this rule may result in problems because many systems reject such kind of hostnames.

    Hope you get something out of this explanation.

    EDIT

    On further investigation on the issue, I came upon this wonderful post which I suppose clarifies the usage of underscore in hostnames:

    http://networkadminkb.com/KB/a156/windows-2003-dns-and-the-underscore.aspx

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