Rules to declare variable
C++ imposes fairly strict rules on how you can
name your variables:
n variable names must begin with a letter
n variable names are "case-sensitive" (i.e., the variable
"myNumber" is different from the variable
"MYNUMBER" which is different from the variable
"mYnUmBeR")
n variable names can't have spaces
n variable names can't have special characters
(typographic symbols, such as &, %, $, £ etc.)
Variables type
n A variable type is a description of the kind of
information a variable will store.