Why Text Messages Are Limited To 160 Characters

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.

Comments

Re:no, its because 160

[Anonymous Coward]

it also happens to be precisely 2 lines of text on a good old 80 character wide terminal.

Re:no, its because 160

[SgtPepperKSU]

is the bastard offspring of the union of the hexdecimal and the decimal, literally 0xF*10

fixed that for you

Are you joking?
0x10*10...

Re:Why text messages instead of email?

[Sockatume]

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:no, its because 160

[jellomizer]

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

Re:SMS vs email

[Rob Kaper]

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.

Getting 160 chars in 128 bits.

[pavon]

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, expecting to find some snazzy compacting algorithm for a non power-of-two alphabet.

Re:Getting 160 chars in 128 bits.

[evanbd]

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).

Re:SMS vs email

[Dan East]

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.

BINGO!

[wonkavader]

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!

[OlRickDawson]

http://en.wikipedia.org/wiki/Punched_card 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!

[earlymon]

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.

Re:Lame Typing

[Achromatic1978]

You'd like to believe it was your Jesusphone being that intelligent, but in reality, the SMS standard has supported message concatenation for at least the last ten years, if not since its inception. My Nokia 2110e could turn it on and off, and you'd see the little counter for "remaining characters" go from 160 to 470 or so.

Silly me.

[hrimhari]

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).

How they got more characters.

[nilbog]

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.

Re:Why were CD's 650MB/72 Minutes?

[RKThoadan]

Snopes says undetermined on that one... http://www.snopes.com/music/media/cdlength.asp

Which is why iPhone texts are ANNOYING

[blahbooboo]

Mind you, my iPhone has no 160 character limit, I'm sure other smart phones just piece together the rapid recieving of messages in to one while the "dumb" phones display them in 160 character chunks.

I absolutely hate when my iPhone friends text me. I end up getting this stream of text messages that are received backwards and cause a lot of hassle just to understand the message on my cell phone.

It would be nice if the iPhone limited texts to 160 characters for those of us without the jesus phone (or a smart phone that supports it).

Oh wait... that's probably why Jobs did that :)

Makkonen vs. Hillebrandt

[Rovaani]

Hillebrandt is not the only one claiming to have invented SMS. Another contender is Finnish Matti Makkonen

Re:I'll Be Damned

[nomorecwrd]

Actually, SMS is like a "stowaway" of a signal your cell must receive from time to time.
So the "real" cost of a SMS is 0.000000.

This is a broadly known fact.

Years ago, here in Chile anyway, SMS where free of charge.
Now is pure profit. (about 8ct/SMS at current exchange)

Re:no, its because 160

[waddleman]

It's a long fail.

Re:Why text messages instead of email?

[SlashDotDotDot]

'To lunch' has been a legitimate verb far longer than people have been, *ahem*, texting.

Re:Standards that won't go away

[againjj]

Snopes. It also mentioned the space shuttle that another responder mentioned.

Re:I'll Be Damned

[Mr2001]

Well let's see. You claim the cost per text is zero. Obviously that's not true since maintenance plus electricity for the towers costs money, but it's obviously quite cheap. So anyway..... my cellphone provider charges just 1 cent per text. That's about cheap as a plan can get, since you can't charge less than a penny (half-pennys were discontinued a long time ago).

That's impressive. Who's your cell phone provider and what sort of package do you need to get that deal? The carriers I know of charge 15 to 20 cents per message (although you can get a discount on the first N messages with a package).

That was hiliarious. The U.S.P.S. is losing money year-after-year and only survives because of taxes drawn from out of our paychecks (see my previous post).

No, that's completely false. If someone told you that, they were lying.

"The Postal Service is a self-sufficient agency. The cost of postal operations, including the costs to extend service to an additional 1.2 million new deliveries in 2008, must be financed by the revenue generated from the sale of postal products and services." (link)

And when I have something important to ship, I definitely don't use the government company. Instead I go to one of the private companies because (1) they cost less (2) they don't lose stuff and (3) if they did it's insured for free (upto $100). Oh and (4) they are the only ones who offer overnight package service; the government does not.

And when you need to send a letter, return a warranty card, pay a bill... do you use FedEx or UPS? I sure hope not: it'd cost much, much more and probably be less reliable. Sending packages is one thing, but private companies simply cannot provide the same service as the USPS for regular mail.

I can't think of a single government company that is as efficiently-run as its commercial counterpart.

That's because you're deliberately ignoring the prime example.