these are based integers
these are literals of VHDL
e.g. Decimal integers: 1 42 153_1203
Based integers: 2#1_0010# 16#F001D#
Characters: ’0’ ’1’ ’X’
Strings: "101011" "XXXXXX"
Bit string literals: B"1001_0101" X"95"
mean "10010101"
Underscores added for readability are ignored