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Why Text Messages Are Limited To 160 Characters 504

Posted by Soulskill
from the how-many-characters-do-you-really-need dept.
The LA Times has a story about Friedhelm Hillebrand, one of the communications researchers behind efforts to standardize various cell phone technologies. In particular, he worked out the 160 character limit for text messages. "Hillebrand sat at his typewriter, tapping out random sentences and questions on a sheet of paper. As he went along, Hillebrand counted the number of letters, numbers, punctuation marks and spaces on the page. Each blurb ran on for a line or two and nearly always clocked in under 160 characters. That became Hillebrand's magic number ... Looking for a data pipeline that would fit these micro messages, Hillebrand came up with the idea to harness a secondary radio channel that already existed on mobile networks. This smaller data lane had been used only to alert a cellphone about reception strength and to supply it with bits of information regarding incoming calls. ... Initially, Hillebrand's team could fit only 128 characters into that space, but that didn't seem like nearly enough. With a little tweaking and a decision to cut down the set of possible letters, numbers and symbols that the system could represent, they squeezed out room for another 32 characters.
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Why Text Messages Are Limited To 160 Characters

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  • by eldavojohn (898314) * <[moc.liamg] [ta] [nhojovadle]> on Monday May 04, 2009 @12:18PM (#27816909) Journal
    And all this time I was almost certain that it was based on sound scientific research proving that 160 characters was the maximum amount of text a cell phone user could read before completely losing interest.
    • by Anonymous Coward on Monday May 04, 2009 @12:22PM (#27816955)

      Technically, it was the largest number that Hillebrand could count to in his mind before losing track.

    • Re: (Score:2, Funny)

      by zappepcs (820751)

      Are you kidding? They lose interest based on who it's from long before any reading of text messages is required.... except for mobile twitterers. Nobody can explain that.

    • by JeffSpudrinski (1310127) on Monday May 04, 2009 @12:23PM (#27816967)

      The few times I've tried messaging from my cell phone, my thumbs cramp after about 50 characters, so the "limitation" never affects me.

    • by Red Flayer (890720) on Monday May 04, 2009 @12:23PM (#27816969) Journal
      tl;dr
    • by bunratty (545641) on Monday May 04, 2009 @12:24PM (#27816989)
      I guess you had something interesting to say on that second line, but I lost interest at the end of the first.
    • by Anonymous Coward on Monday May 04, 2009 @12:25PM (#27817005)

      And all this time I was almost certain that it was based on sound scientific research proving that 160 characters was the maximum amount of text a cell phone us...

      I totally lost interest past that.

    • Re: (Score:2, Funny)

      And all this time I was almost certain that it was based on sound scientific research proving that 160 characters was the maximum amount of text a cell phone user could read before completely losing interest.

      I don't get your point. All I read was: "And all this time I was almost certain that it was based on sound scientific research proving that 160 characters was the maximum amount of text a cell phone u".

    • by jcr (53032)

      160 characters was the maximum amount of text a cell phone user could read before completely losing interest.

      Perhaps it's a conditioned response to having only short messages available.

      -jcr

  • is the bastard offspring of the union of the hexdecimal and the decimal, literally 16*10

    all of us techies straddle these two worlds. 160 is our numerology of frustration, the techie 666

    • by Anonymous Coward on Monday May 04, 2009 @12:25PM (#27817007)
      it also happens to be precisely 2 lines of text on a good old 80 character wide terminal.
      • by jellomizer (103300) on Monday May 04, 2009 @12:33PM (#27817113)

        80 characters (bytes) just happened to be how many punched you can normally fit on a standard punch card.

        • BINGO! (Score:5, Informative)

          by wonkavader (605434) on Monday May 04, 2009 @12:44PM (#27817271)

          And a full-screen terminal (3270, etc.) is really just 25 punch cards. You press "Enter" and they get submitted. Your batch processes and the system returns you 25 punch cards which your smart 3270 punch card reader/editor displays for you.

          Punch cards are based on the civil-war-era dollar bill because there were already machine to count and stack dollar bills.

          Punch cards were IBM's most profitable product ever until the introduction of the IBM PC.

          • Re:BINGO! (Score:5, Informative)

            by OlRickDawson (648236) on Monday May 04, 2009 @01:01PM (#27817557)
            http://en.wikipedia.org/wiki/Punched_card [wikipedia.org] Punch cards predate the computer, because they were used in loom machines to generate paterns. The punch cards were later used for statistical purposes. IBM was already selling statistical machines that used the punch cards before the computer. The reason that IBM was able to grab the market instead of Univac, is because IBM's computers was compatible with the punch cards that the corporations already had.
            • Re:BINGO! (Score:4, Informative)

              by earlymon (1116185) on Monday May 04, 2009 @02:29PM (#27818893) Homepage Journal

              The parent is mostly correct regarding the Civil War and the wikipedia entry is lacking. I can't speak for the parent, but I am aware of this from a portion of James Burke's Day the Universe Changed series.

              The punch card reading technology came from looms, sure - unless you count music boxes. Looms used continuous punched paper first - the music box again.

              The punch card was used in 1880 US Census - that statistical application that you talk about - not so much because of the machinery to handle it - it was because of its size, and that was by design.

              There were a glut of older cash drawers that could used for keeping the stacks neat and/or in sorted piles.

              So, you've got the computing machinery and techniques in place - do you use a strip or a card? When using a card, do you contract to build new carrying boxes or do you re-purpose the vastly available and nearly-useless-therefore-cheap surplus cash drawers? Note the supporting statement from your own wiki reference:

              The Columbia site says Hollerith took advantage of available boxes designed to transport paper currency.

              I not sure about your analysis of why IBM grabbed the market over Univac. I do recall that in the old days, there was IBM and then there was BUNCH - Burroughs, Univac, NCR, Control Data and Honeywell.

              I think if you look back to 1929 and thereafter (read: the rebuilding of American business after the Great Crash), IBM was the key producer of cards and card-related technologies. So the real reason that IBM computers were compatible with the cards that corporations had was more likely that they were IBM cards in the first place.

              IBM's history stretches continuously back to the 19th century, and its name means International Business Machines. Univac came from Remington Rand in 1950 - a large industrialist that made, among other things, typewriters, as I recall. So from the Great Crash to 1950, you have nothing from Univac to buy - but you do have IBM. Now computers come along, and the one company that survived the crash and is helping your business get Really Organized is selling you a new type of Business Machine - supply compatible with some of their old. Or - you could buy a Univac.

              I could be wrong - I don't think I am, though, for what that's worth.

        • by The Evil Couch (621105) on Monday May 04, 2009 @02:15PM (#27818715) Homepage
          That means that 160 characters makes perfect sense! You'd get 160 characters if you used both sides of the punch card!
  • by loshwomp (468955) on Monday May 04, 2009 @12:24PM (#27816985)

    The real question should be "Why are we still using ancient text messages instead of regular email?" All of my friends in Japan regularly do full-on email on their phones, and only have a vague-if-any notion of what a regular "text message" is elsewhere. 160-character limit? That is *so* 1990s.

    • by Krneki (1192201) on Monday May 04, 2009 @12:30PM (#27817083)
      Because you can charge for SMS, while emails needs full Internet access. And they don't want to give us cheap Internet access.
    • by Sockatume (732728) on Monday May 04, 2009 @12:32PM (#27817103)
      The account's set up with your phone number, uses the same user identifier, travels with the phone number, and there's a billing infrastructure for it. Meanwhile the vast majority of phone users don't even have packet data plans. It's operator inertia, basically.
    • Re: (Score:3, Insightful)

      by drsquare (530038)

      Because phone Internet access is incredibly expensive compared to text messages. Japan isn't a good example, they love any expensive gimmick.

    • by Speare (84249) on Monday May 04, 2009 @12:36PM (#27817159) Homepage Journal
      I think the Japanese and Chinese markets have completely ignored the SMS thing because of the character sets involved. If 160 latin characters can be compressed into about 128 bytes, how many hanzi can fit? Maybe forty? That's probably enough for some thoughts like "Meet you at train station at 11am" but nothing really more complicated than that.
      • by julesh (229690) on Monday May 04, 2009 @12:59PM (#27817523)

        If 160 latin characters can be compressed into about 128 bytes, how many hanzi can fit? Maybe forty?

        Probably more like 64; two bytes is usually enough to represent just about anything. A clever encoding scheme might squeeze as many as 80 in. OTOH, each of those characters carries more information than a single character of English text. Not sure about Japanese, but most common Chinese words [pandagator.info] are only two characters long, so being able to include fewer characters shouldn't be a real issue.

        • Re: (Score:3, Interesting)

          by jabithew (1340853)

          This is reminding me of Shannon Entropy [wikipedia.org]. I'm guessing human thought contains a similar amount of bits whether it's expressed in Chinese (high bits/character) or French (low bits per character).

      • by Aladrin (926209) on Monday May 04, 2009 @01:00PM (#27817537)

        128, at least, assuming UTF8. And the Japanese can say things a lot more compactly than we can:

        èããY - I woke up.
        åå¾OEãé£Yãã¾ã--ãY - I ate in the afternoon.
        éf½éYã®åé"ãé話ã'ã--ã¾ã(TM) - I am talking on the telephone with my friend in Tokyo.

        (Of course, the above won't come through correctly on Slashdot, but they are about half the characters of the English phrases.)

      • Re: (Score:3, Insightful)

        by TheRaven64 (641858)
        Kanji is much denser than English text. You need a minimum of 4 characters plus a space per word in English (the average is closer to 5-6, meaning 7 bytes - 5.25 octets with a 6-bit byte). In contrast, a lot of common words in Chinese or Japanese need only one or two ideographs. These can all be represented in a 16-bit character set, and probably closer to 14 bits. This means that the 1024-bit header for SMS can carry something like 70 words in Japanese or Chinese, but only about 25 in English.
    • Re: (Score:3, Informative)

      by XxtraLarGe (551297)

      "Why are we still using ancient text messages instead of regular email?"

      I can't speak for everybody, but I use a Tracfone. Talking costs $.10 a minute, but text messages only cost me $.03 per message. I pay $6 per month for my phone (it's mostly for emergencies), and communicating by text message helps to spread out the amount of use I can get each month. One thing that's even better is the fact that my wife or I can text each other from our e-mail. It's easier if I'm at the store and my wife texts me to pick up eggs, milk, what-have-you, so I'll only use $.03 to get the same

  • SMS vs email (Score:5, Interesting)

    by pieterh (196118) on Monday May 04, 2009 @12:24PM (#27816995) Homepage

    An exercise in cartel economics: compare the costs of SMS traffic vs. email traffic and explain the differences. :-)

    • Re:SMS vs email (Score:5, Informative)

      by Rob Kaper (5960) on Monday May 04, 2009 @12:37PM (#27817177) Homepage

      Differences:

      - SMS is available: it's built-in, e-mail is not present on every phone and relies on a third-party service provider plus settings

      - SMS is faster: because there is no GPRS/TCP/IP/SMTP/IMAP/POP connection and transfer overhead

      - SMS is clean: no risk of having to retrieve large attachements, hardly any spam due to sender costs

      - SMS is cheaper: most plans offer a sufficient amount of free messages a month for most users, e-mail requires an additional GPRS data plan

      YMMV but SMS is not as bad as some people claim.

      • Re: (Score:3, Funny)

        by Just Some Guy (3352)

        SMS is available: it's built-in, e-mail is not present on every phone and relies on a third-party service provider plus settings

        Translation: phone providers suck for not broadly offering decent services.

        SMS is faster: because there is no GPRS/TCP/IP/SMTP/IMAP/POP connection and transfer overhead

        And a Prius is faster than a Ferrari because it doesn't have those big, heavy brakes.

        SMS is clean: no risk of having to retrieve large attachements, hardly any spam due to sender costs

        Translation: it's not a bug, it's a feature!

        SMS is cheaper

        ROTFLMAOWTFBBQ!1!

        Assuming you're serious, data plans here start at $30/month for browsing + messaging + whatever else you can send over a socket. Unlimited texting is $20, or you can pay $0.25 as you go. Send 3 text messages a day and it's cheaper just to buy the best plan.

    • Re:SMS vs email (Score:5, Informative)

      by Dan East (318230) on Monday May 04, 2009 @12:42PM (#27817251) Homepage Journal

      Here's what's ridiculous. I have a Blackberry, and do not have an SMS plan with my carrier, thus each text costs me 25 cents to send. Receiving SMS is free and unlimited. I have an unlimited data plan for Blackberry, so I simply send emails using the carrier email SMS gateways for "free". The only downside is that the recipient cannot directly reply to my message. Here's the stupid part. The amount of bandwidth, processing, and inter-service gateways my emails have to pass through must require at least 100 times the resources of sending an actual SMS. The final kicker is that even if I keep my actual message under 160 chars, they are usually broken up into more than one SMS message because of the header attached by the SMS gateway that contains my email address, etc.

  • Hmm, reminds me of the joke about why the standard railway gauge is 4'8.5" -- going back to the width of ancient roman roads. There's also the (urban legend?) that legal size paper (In the US) is 8.5"x14" because that's the largest sheet that could fit into a pony express bag without folding.

  • by XPeter (1429763) * on Monday May 04, 2009 @12:34PM (#27817139) Homepage

    bc whn u txt u typ lik ths so ther isnt any ned fr mor thn 160 chars. I'm a teen, I know best.

  • My 17 yr old (mostly stupid) step-daughter is already using what looks like huffman coding in her text messages... why doesn't some genius study that.

    • by jcr (53032) <jcr@[ ].com ['mac' in gap]> on Monday May 04, 2009 @01:30PM (#27818017) Journal

      My 17 yr old (mostly stupid) step-daughter

      That remark gives me a far more negative opinion of you than of her.

      -jcr

      • by UncleTogie (1004853) on Monday May 04, 2009 @03:14PM (#27819601) Homepage Journal

        Actually, I find the honesty refreshing.

        The ones I have a low opinion of are the parents that insist "My child is really smart and beautiful! It's the school/teacher/environment to blame for my child's inability to multiply single-digit numbers without a calculator!"

        Mayhaps if more parents took a realistic view of their crotch-fruit, we wouldn't have the self-absorbed, narcissistic bozos who feel entitled to do whatever they want.

        ...and before anyone asks, yes, I *am* a parent.

        • by EvolutionsPeak (913411) on Monday May 04, 2009 @04:32PM (#27820775)

          Well it's easier for the GP since it is some other guys crotch-fruit, not his.

        • by jcr (53032) <jcr@[ ].com ['mac' in gap]> on Monday May 04, 2009 @07:13PM (#27823355) Journal

          Actually, I find the honesty refreshing.

          Actually, excusing bad behavior as "honesty" is something I'm rather tired of. Disparaging his wife's child like that shows me that he's someone lacking in empathy or compassion.

          -jcr

          • by UncleTogie (1004853) on Tuesday May 05, 2009 @01:10AM (#27826753) Homepage Journal

            Actually, excusing bad behavior as "honesty" is something I'm rather tired of.

            Which makes her less stupid how?

            I have friends that're dumb, and are the first to tell you "Ah ain't up on all that-thar book-larnin'..." I don't think any less of them for it, and they're some solid friends. Y'know, the kind you could trust at your back when the going gets nasty. Another fave anecdotal moment:

            My dad retired to a rural area. A young couple {friends of the family} was getting married, and dad decided to give 'em a book on managing your budget. However, the young wife, barely 18, refused the gift. Dad asked why, and she explained that her husband, Reed wouldn't use it. Her exact words:

            "Y'see, Reed don't read."

            -blink-

            Note, that wasn't "Reed can't read", or "Reed doesn't read much"... Now, you can call me ill-mannered for saying that Reed is probably not the brightest bulb in the marquee, but I'm telling you, some people are just plain dumb, whether it's politically correct to say so or not. That's the problem with the whole PC movement; you can polish a turd all you want, but it's still a turd. BTW, I'm not moderately hearing-impaired, I'm mostly deaf... and have no problems saying so.

  • Bad article (Score:5, Insightful)

    by Sockatume (732728) on Monday May 04, 2009 @12:39PM (#27817207)
    The article states outright that the 160-character limit came before Hillebrand's "typewriter experiment", and that the experiment actually about because of an argument between Hillebrand and a coworker about whether 160 characters was sufficient for a sensible message. This meshes with what we already know about SMS, namely that it could never have been much more than 128 characters for technical reasons. Quite why the article structures its opening to suggest that Hillebrand pulled the number out of his arse after some typewriter time is a mystery.
  • by pavon (30274) on Monday May 04, 2009 @12:40PM (#27817227)

    For those that were wondering how they got 160 characters into 128 bytes (6.4 bits/char), they didn't. The increased the length of the frame to 140 bytes, which is is 160 characters using a 7 bits/char. Curiosity forced me to look this up [wikipedia.org], expecting to find some snazzy compacting algorithm for a non power-of-two alphabet.

    • by evanbd (210358) on Monday May 04, 2009 @01:14PM (#27817757)

      There are some straightforward compaction algorithms for non power-of-two sizes. The simplest approach is to take n symbols in your alphabet, treat it as an n-digit number base b (the number of different symbols), and convert that to base two. You'll use at most ceiling(n * log2(b)) bits.

      You can be more sophisticated by using a compression algorithm of some sort (Huffman with a standardized dictionary, for a simple example). Anything that does better than the above n * log2(b) will produce a variable length output, though, which means that while you could usually fit more than 160 characters into 140 bytes, sometimes the limit would be lower (since rare characters take more bits to encode).

  • by viralMeme (1461143) on Monday May 04, 2009 @12:42PM (#27817255)
    How about tokenizing [classic-games.com] commonly used words and sending that, ne byte per word ?
    • Re: (Score:3, Insightful)

      by tirerim (1108567)
      Because you only get 256 different words that way? There are a lot more commonly used words than that, and then you're left with no way to spell out the uncommonly used words, either. You could use two bytes per word... but that's basically what txtspk is anyway, only with variable compression, such that the most common words get compressed down to a single byte (often as part of a longer abbreviation).
      • Re: (Score:3, Funny)

        by Sockatume (732728)
        I think that 256 words should be enough for everyone. It's not like ???INEXPRESSABLE CONCEPT ERROR????
  • by ducomputergeek (595742) on Monday May 04, 2009 @12:56PM (#27817481)

    Because that was the amount of space required to fit Beethoven's 9th Symphony on one side of a disc. And the researcher apparently loved that Symphony and hated having to switch to different sides of a tape or record.

    It's always interesting to the reasons why. Sometimes there is a purely logical reason, and other times, it's just because.

  • Silly me. (Score:4, Informative)

    by hrimhari (1241292) on Monday May 04, 2009 @01:24PM (#27817917) Journal

    Here I was, in my dumb ignorance caused by blind experience on the field, thinking that the limit was actually caused by the magic 255 number less protocol overhead (result: 140) plus 7-bit encoding compression (result: 160).

  • In 2009 (Score:5, Funny)

    by Tarlus (1000874) on Monday May 04, 2009 @01:29PM (#27817993)
    And all these years later in 2009, I still have
  • by nilbog (732352) on Monday May 04, 2009 @01:30PM (#27818011) Homepage Journal

    If anyone is interested - the way they got more characters available was by cutting down characters to 7bits instead of the normal 8, thus limiting the possible characters to 128.

    1120bits/7bits = 160 characters.

  • At 3600 baud, even (Score:3, Informative)

    by Animats (122034) on Monday May 04, 2009 @02:00PM (#27818465) Homepage

    In AMPS, the cell phone technology being described, there's a 3600 baud control channel shared between all the phones in a cell. Text messages had to be crammed into that. Voice was analog FM, with the control channel telling the handsets which voice channel to use.

    That's why SMS is so data-limited. The data channel was tiny.

  • by Rovaani (20023) on Monday May 04, 2009 @02:14PM (#27818695)
    Hillebrandt is not the only one claiming to have invented SMS. Another contender is Finnish Matti Makkonen [irishtimes.com]

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