SMS (Short Message Service), commonly referred to as "text messaging," is a service for sending short messages of up to 160 characters (224 characters if using a 5-bit mode) to mobile devices, including cellular phones, smartphones and PDAs.
SMS is similar to paging. However, SMS messages do not require the mobile phone to be active and within range and will be held for a number of days until the phone is active and within range. SMS messages are transmitted within the same cell or to anyone with roaming service capability. They can also be sent to digital phones in a number of other ways, including:
- From one digital phone to another
- From Web-based applications within a Web browser
- From instant messaging clients like ICQ
- From VoIP applications like Skype
- From some unified communications applications.
Typical uses of SMS include:
- Notifying a mobile phone owner of a voicemail message
- Notifying a salesperson of an inquiry and contact to call
- Notifying a doctor of a patient with an emergency problem
- Notifying a service person of the time and place of their next call
- Notifying a driver of the address of the next pickup
- Enhanced messaging service (EMS), an adaptation of SMS that allows users to send and receive ringtones and operator logos, as well as combinations of simple media to and from EMS-compliant handsets.
In recent years, SMS spam has become an issue for some users, as has SMiShing, a security attack in which the user is tricked into downloading a Trojan horse, virus or other malware onto a cellular phone or other mobile device.
Users can send messages from a computer via an SMS gateway. SMS gateways are Web sites that allow users to send messages to people within the cell served by that gateway. They also serve as international gateways for users with roaming capability.