Notes on formal languages: alphabets, strings and languages
An alphabet is any set of finite symbols such as a and b. For example, the alphabet Σ = {a, b} is an alphabet that contains the strings that can be built by combining a and b and the alphabet Σ = {0, 1} is the an alphabet that contains the strings that can be built by combining 0 and 1. Symbols such as a and b put together to form something like bbaa are called strings. ...