Unicode Table:

https://unicode-table.com/en/#control-character

References:

https://en.wikipedia.org/wiki/Variable_(computer_science)

https://en.wikipedia.org/wiki/Data_type

JLS 4.2.3. Floating-Point Types, Formats, and Values
https://docs.oracle.com/javase/specs/jls/se11/html/jls-4.html#jls-4.2.3

JLS 3.10.2. Floating-Point Literals
https://docs.oracle.com/javase/specs/jls/se11/html/jls-3.html#jls-3.10.2