The definition of names for Calculations, variables or functions has some simple rules. The name we choose must start with a letter in the range a-z, underscore character (_) or above ASCII code 128. Numeric or alphanumeric digits can follow. As with standard symbols, are not case sensitive.
Also in case we need variables that broke the above rules and contain spaces we can create such variables if enclose them in back-quots (`) characters. e.g. `February Income`. This kind of variables are mostly useful to the calculating part of the program. These variables are not case sensitive too.