Signed numbers use the leftmost bit to represent the sign and the remaining bits to represent the magnitude. Unsigned numbers use all the bits to represent the magnitude of the number.
long and short just indicate the size (number of bits) of the bit
pattern used to represent a number. long has more bits (64)while short has fewer bits (16).
Java primitive integral data types are all signed with the exception of char (for which a sign has no meaning anyway).
[This message has been edited by JUNILU LACAR (edited June 22, 2001).]