Computers process numbers using arithmetic and logic (which amount to the same thing). Processing text, however, requires at least two levels of abstraction. Firstly, a definition of a textual atom — informally a character. Secondly, a definition of a textual unit — typically called a string. A string is an ordered list of characters.
Therein lies a whole field of computer science. From a practical point of view, implementing text has become much easier with Unicode. Different character sets was one of the more awful aspects of dealing with text. (Remember CP-1252?)