lexical structure of a programming language is the set of elementary rules that
specifies how to write programs in that language. It is the lowest-level syntax
of a language. The Lexical structure specifies variable names, the delimiter
characters for comments, and how one program statement is separated from the
type the command in lowercase.
ignores spaces that appear between tokens (identifiers, operators, punctuator,
constants and keywords) in programs.
a “//” and the end of a line is treated as a single line comment and is ignored
semicolons to explicitly mark the ends of statements.
literal is a data value for variable that appears directly in a program.
as reserved words, These words cannot used as identifiers in the programs