What is SMS?

SMS is an acronym that stands for Short Message Service, more commonly known in some places as text messaging or "texting." This technology is a way to wirelessly send messages of up to 160 characters between cell phones or other devices. SMS is not the only texting technology, but it is the standard used by most major cell phone networks.

When a person sends an SMS message, he or she usually uses her telephone keypad or physical or on-screen keyboard to type out a message. The user selects the recipient's phone number (or other address information) and clicks "send." From there, the message is sent to a short message service center (SMSC), which stores it and tries to send it on to the recipient. If the receiver is on another network, the message may travel through a gateway mobile switching center (MSC), which allows the different systems to communicate. The SMSC usually stores the message if it cannot be sent immediately and retries later; in some cases, however, the message will be dropped if it is not delivered successfully on the first attempt.

Messages can be sent without the voice function of a cell phone being activated because it uses the control channel. This pathway is always active whenever the phone is turned on, and regularly sends and receives signals from the nearest cellular tower. The control channel is also used to set up voice calls, find the phone's location, and make sure the service is working correctly.

A text message is limited to 160 Latin-based characters because the format of the signal used to transmit the data. This signal can only carry 140 bytes, which works out to 160 characters of 7 bits each. Non-Latin texts, such as those in Arabic or Chinese, are limited to 70 characters.

The limited number of characters that can be sent via SMS has led to the development of a digital shorthand to communicate more information quickly. This text lingo often drops vowels and superfluous letters, in addition to replacing words or sounds with representative numbers or single letters. For example, a person might type "did u c wut he askd me 2 do? 4 shme!" to represent the sentence, "Did you see what he asked me to do? For shame!" In most cases, grammar, capitalization, and punctuation rules are ignored. Some abbreviations and symbols, like "LOL" for "laugh out loud" or the smiley face emoticon — :) — have made their way into other online communication, including emails and discussion forums.

Many text messages are sent from person to person, often as part of an electronic conversation. This is also known as point-to-point (SMS-PP) messaging, and is used primarily for communications between individuals. In many cases, messages can also be sent to a cell phone — and sometimes received from one — via the Internet, using an email-to-SMS or web-based service.

Messages may also be sent to many devices within a specific geographical region. Regional messaging, or SMS-CB, can be used to broadcast public announcements or for alerts from a cell provider regarding the coverage area. Text messaging can also be used to send advertising or application related messages to specific users or groups of users. For example, a television station might offer a service in which a viewer can provide the station with his or her cell phone number; in return, the station will send breaking news alerts via text to all users who've signed up for the service. A drugstore might invite patients to register their phone numbers when they submit prescription information, allowing the store to text patients when those prescriptions need to be refilled and when they're ready for pickup.

SMS has also been used by a number of television networks and corporations to encourage consumers to interact with a product. Some television competition programs, for example, allow viewers to vote for their favorite participants via text. European television has pushed the idea even further, encouraging viewers of some shows to control the actions of characters on screen using their cell phone's SMS capabilities.

Some online services have integrated SMS capability to allow for information to be accessed easily through a cell phone. By texting a certain number, for example, a cell phone user may receive information ranging from local weather to the location of a bus station. Social media sites like Twitter™ and Facebook allow users to post messages to their accounts and receive updates by text.

In politics, text messaging has also been used to send messages from candidates to potential voters. Donations to candidates or charitable organizations can be made via text. SMS has been used to organize political resistance and social unrest. Although other social media technologies have taken on more of this role, SMS is still a very effective way to spread messages among people, especially in countries where the Internet and other forms of communication are more restricted.

The SMS protocol began with Global System for Mobile Communications (GSM) standards created in 1985. It was not commercially available until 1993, and not all cellular service providers offered the service. Its popularity grew throughout Europe and in Asia throughout the 1990s and 2000s; one of the main drivers was it's price, which was often much lower than even a brief voice call.

In 2000, fewer than 20 billion messages were sent; by 2010, that number had grown to 6.1 trillion. More than 70% of adult cell phone users in the US reported that they used their phones for text messaging in 2010. SMS is especially popular with younger phone users in many places.

The delivery of a text message is not guaranteed, with up to 5% of messages getting lost in transmission or delivered long after they are sent. In general, wireless providers consider SMS to be lower priority than voice communications, and because of this, there has been criticism of text messaging as a means of delivering emergency notifications to the public.

Other texting problems can occur when the receiving individual’s wireless provider does not offer the same services as that of the sender. The majority of wireless providers in North America use a 7-bit alphabet for text messaging. An 8-bit messaging system supported by some providers allows users to send image files in addition to text. Receiving an 8-bit message via a 7-bit provider is likely to result in a garbled string of nonsense text for the end user.

As the popularity of SMS has grown, so has the concern about people using their phones while doing other things, like walking or driving. In the US, many states have laws against drivers using handheld cell phones for any reason, including making voice calls or texting. As of 2012, 39 states and the District of Columbia ban all drivers from texting while driving.