Curious about Twitter's 140 characters.

[janeslogin]

Based upon what I recall from my computer science classes I would expect something near, but probably not exactly, 128 or 256.

Do you know the explanation for the 140?

[willia4]

Twitter was originally designed to be used primarily via text messages (SMS). Text messages, of course, have a maximum length of 160 characters (Cite).

So 140 characters left enough room for them to add in 20 characters worth of “Tweet from @SoAndSo” (or however they phrase it. I haven’t actually used twitter via SMS since I got a smart phone a few years ago).

[Simplicio]

IIRC, the limit on SMS messages was 140 bytes. Course, that just raises the question…

[Mahaloth]

Wikipedia has it.

The messages were initially set to 140-character limit for compatibility with SMS messaging, introducing the shorthand notation and slang commonly used in SMS messages. The 140-character limit has also increased the usage of URL shortening services such as bit.ly, goo.gl, and tr.im, and content-hosting services, such as Twitpic, memozu.com and NotePub to accommodate multimedia content and text longer than 140 characters. Twitter uses bit.ly for automatic shortening of all URLs posted on its website.

[Earl_Snake-Hips_Tucker]

Now, if we can just find out what the character limit on SMS messaging is. . . .

[Blakeyrat]

It’s worth noting that Twitter is technically capable of sending longer tweets-- if you use Twitters “retweet” feature, then look at the retweet from another (non-Twitter-owned) client, the text of the tweet is: “RT @original_username original_tweet_content”. Meaning, if the original tweet was 140 characters, a retweet of it can be 140 + 3 (“RT “) + 20 (”@username”), 163 characters.

So basically, it’s arbitrary at this point.

[fiddlesticks]

I have discovered a truly marvelous discussion of this, which this margin is too narrow to contain.

[Sunspace]

@Earl_Snake-Hips_Tucker

Now, if we can just find out what the character limit on SMS messaging is. . . .

@Wikipedia

Transmission of short messages between the SMSC and the handset is done whenever using the Mobile Application Part (MAP) of the SS7 protocol. Messages are sent with the MAP MO- and MT-ForwardSM operations, whose payload length is limited by the constraints of the signaling protocol to precisely 140 octets (140 octets = 140 * 8 bits = 1120 bits). Short messages can be encoded using a variety of alphabets: the default GSM 7-bit alphabet, the 8-bit data alphabet, and the 16-bit UTF-16 alphabet.[30] Depending on which alphabet the subscriber has configured in the handset, this leads to the maximum individual short message sizes of 160 7-bit characters, 140 8-bit characters, or 70 16-bit characters (including spaces). GSM 7-bit alphabet support is mandatory for GSM handsets and network elements,[30] but characters in languages such as Arabic, Chinese, Korean, Japanese or Cyrillic alphabet languages (e.g. Russian, Serbian, Bulgarian, etc.) must be encoded using the 16-bit UTF-16 character encoding (see Unicode). Routing data and other metadata is additional to the payload size.

Larger content (concatenated SMS, multipart or segmented SMS, or “long SMS”) can be sent using multiple messages, in which case each message will start with a user data header (UDH) containing segmentation information. Since UDH is part of the payload, the number of available characters per segment is lower: 153 for 7-bit encoding, 134 for 8-bit encoding and 67 for 16-bit encoding. The receiving handset is then responsible for reassembling the message and presenting it to the user as one long message. While the standard theoretically permits up to 255 segments,[31] 6 to 8 segment messages are the practical maximum, and long messages are often billed as equivalent to multiple SMS messages. See concatenated SMS for more information. Some providers have offered length-oriented pricing schemes for messages, however, the phenomenon is disappearing.

The character limit on SMS messaging was set because their text travels through spare data bits embedded in regular (digital, GSM) cellphone transmissions, not though “data connections”. This is why pretty much all GSM phones can SMS, and you don’t need a data plan to do so. SMS was later added to other digital standards–CDMA for certain, and I believe iDEN as well, but I could be wrong. I’d be very surprised if the Chinese TD-SCDMA standard didn’t have it.

[jasg]

@fiddlesticks

I have discovered a truly marvelous discussion of this, which this margin is too narrow to contain.

+1!

[Polycarp]

@fiddlesticks

I have discovered a truly marvelous discussion of this, which this margin is too narrow to contain.

Ah, the famous Fermat’s Last Tweet!