SMS stands for Short Message Service. It is a wireless service that enables transmission of messages. ‘Short’ restricts the length of the text message to 160 characters that includes alphabets, number and special characters/symbols. It is widely sent between cell phones or from a PC to a cell phone.
Whether a person is talking over a cell phone or not, it does not matter. The cell phone always talks (sending and receiving information) to the control tower whichever is nearer. It is done through a pathway called control channel.
SMS is basically a store and forward way of transmitting messages through a central short message service centre (SMSC). The SMSC is a combination of hardware and software responsible for the relaying, storing and forwarding of a short message. It means the message doesn’t directly reach the receiver and also the receiver’s cell phone need not be ON or in range. MSC stands for mobile switching centre. The data in mobile networks is routed through a series of MSCs. The transmitted messages are first stored in the SMSC. From here it goes to the tower and the tower sends the message to your phone as little packet of data on the control channel. If the receiver’s phone is switched off or its inbox is full, the SMSC retains the messages until the user receives them. There is also a service called broadcasting in which messages are sent not to one but to a group of people.
The advantages of SMS are that there is privacy; it proves very useful for deaf and dumb people and also less time consuming. One major disadvantage is its inefficiency in delivering messages. When message centre is backed up, it takes long time to deliver messages.