Short code
Common Short Codes shorter than normal numbers which can receive SMS and MMS messages from mobile telephones. They are designed to be shorter to read out and easier to remember than a normal length telephone number.
Short codes are widely used for television voting, ordering ringtones, charity donations and mobile services (such as Google's SMS search service). Messages sent to short code numbers are generally billed at a higher rate than a standard SMS.
Regional Differences
Canada
Codes are 5 or 6 digits in length. Codes starting with 4 are not permitted due to handset incompatibilities.
Codes are 5 digits in length, starting with 6 or 8 (codes starting in 5 and 7 exist, but are reserved for future expansion). Individual network operators may come to an agreement with customers, allowing any number to be used - except for adult content services, which must use codes starting with 69 or 89.
Codes are 5 digits in length. Codes starting with 1 are not permitted.