For example, Linux is an operating system that contains thousands of lines of code, but it started out as a simple program Linus Torvalds used to explore the Intel 80386 chip. In later chapters I will make more suggestions about debugging and other programming practices. Natural languages are the languages that people speak, like English, Spanish, and French. Formal languages are languages that are designed by people for specific applications. For example, the notation that mathematicians use is a formal language that is particularly good at denoting relationships among numbers and symbols.
Chemists use a formal language to represent the chemical structure of molecules.
As I mentioned before, formal languages tend to have strict rules about syntax. Also, H 2 O is a syntactically correct chemical name, but 2 Zz is not. Syntax rules come in two flavors, pertaining to tokens and structure. Tokens are the basic elements of the language, like words and numbers and chemical elements. Similarly, molecular formulas have to have subscripts after the element name, not before.