Character encoding
Given a number of characters of an alphabet, a character encoding is a function that will map each character to a number. This number must be unique and is called code point. In this context, a character is the minimal unit of text that has a semantic value: In alphabets that use letters, this is usually a letter. Early systems, like the telegraph only have a part of all the letters possible. They have only uppercase letters, numbers, and a few extra characters (punctuation, spacing, newline..). The flag alphabet ships use is even more restricted.
Character Encoding Media
Punched tape with the word "Wikipedia" encoded in ASCII. Presence and absence of a hole represents 1 and 0, respectively; for example, "W" is encoded as "1010111".
Hollerith 80-column punch card with EBCDIC character set
