Each mathematical object created by the user is associated
with a name selected by the user. Identifiers begin with an
alphabetic character (upper or lower case) or one of the following three
characters: @, ', _.
Subsequent characters of the identifer must be either digits 
or a character from the above list. The length of an
identifier is limited to 50 characters. Upper and lower case
characters are distinct, thus the identifiers ``myMatrix'' and
``mymatrix'' refer to different user variables.
For example, the following are all legal names in Macaulay.
a'mine
@veronese
my_matrix
m0128
a'
The character @ is used for local variables inside scripts (command files): Inside of a script, @ is expanded to @nn@, where nn is the ``level'' of this script. Thus name conflicts will not occur if all local variables in a script contain a @. See Chapter 11 for details.
Wherever an identifier is expected as a paramter to a command, you may enclose it in curly braces. Therefore, the identifiers ``a_mat'' and ``{a_mat}'' represent the same variable. Curly braces are only required in certain instances, to avoid name conflicts. See section 4.3 for a complete list of these instances.