All application software transmits and receives data within an individual computer. Special communications software is used to send and receive data over networks and using modems.
![Picture](/uploads/4/8/7/3/48736149/6743705.gif?378)
Communications software manages the transfer of data, files and commands between computers. It uses protocols to establish a connection. A protocol is a set of rules that governs the transfer of data between computers. It defines how the information is transmitted and how errors are detected. Two computers must use the same protocols, otherwise the data transfer may be unsuccessful.
![Picture](/uploads/4/8/7/3/48736149/1085223.png?378)
Compression reduces the number of bits required to represent data. It compacts the data so that it takes up less space on a disk and requires less time to download. Compressed data must be decompressed in order to extract the original information. The amount a file is compressed is measured by the compression ratio.
![Picture](/uploads/4/8/7/3/48736149/6259753.jpg?391)
Electronic mail (email) allows communication with other users by sending and receiving electronic messages using a computer. Email messages are often short and are typed quickly. Messages are written offline and sent when the user logs onto the LAN or the Internet. Attachments are computer files sent with email messages, such as image, audio, video or text files.
![Picture](/uploads/4/8/7/3/48736149/2725402.png?396)
Data encryption is used to prevent data from being intercepted and read during transmission. The data is ‘scrambled’ so that it is meaningless to anyone other than the recipient, who uses the same encryption software to convert it back. One popular encryption method is Secure Socket Layer (SSL).