Texting code, also known as SMS or Short Message Service language, is used because early carriers of SMS limited the number of characters per message to 160 letters per message. Users found that by implementing abbreviated codes in place of common words and phrases, they could convey messages more quickly and efficiently. Despite a subsequent rise in predictive text software, many of these codes became mainstays of contemporary text language.
Before the introduction of physical and virtual keyboards to telephones, SMS interfaces required users to press a key several times before their desired letter was displayed. Abbreviations such as "2" for "to" or "too" often were used to reduce the amount of time spent searching for letters for frequently used or long words. This convention was followed with other ease-of-use abbreviations and acronyms for commonly used phrases.
These codes were useful because early phones that employed SMS used telephone keypads in place of traditional keyboards. Each number on a keypad, excluding zero and one, is assigned three to four letters of the alphabet. Initially, these letters designated telephone exchange offices and could form "phonewords" that allowed users to remember phone numbers from advertisements by corresponding the letters of the word and the digits on the keypad.