Encoding is the process of putting a sequence of characters (letters, numbers, punctuation, and certain symbols) into a specialized format for efficient transmission or storage.
Encoding involves the use of a code to change original data into a form that can be used by an external process.
The type of code used for converting characters is known as American Standard Code for Information Interchange (ASCII), the most commonly used encoding scheme for files that contain text. ASCII contains printable and nonprintable characters that represent uppercase and lowercase letters, symbols, punctuation marks and numbers. A unique number is assigned to some characters.
The standard ASCII scheme has only zero to 127 character positions; 128 through 255 are undefined. The problem of undefined characters is solved by Unicode encoding, which assigns a number to every character used worldwide. Other types of codes include BinHex, Uuencode (UNIX to UNIX encoding) and Multipurpose Internet Mail Extensions (MIME).
Encoding is also used to reduce the size of audio and video files. Each audio and video file format has a corresponding coder-decoder (codec) program that is used to code it into the appropriate format and then decodes for playback.
Encoding should not be confused with encryption, which hides content. Both techniques are used extensively in the networking, software programming, wireless communication and storage fields.