The following are the rules for symbol construction:
The first character of a symbol must be either a letter, a question mark (?), an underline (_), a dollar sign ($), or a period (.).
All other characters in the symbol may be any alphanumeric character, dollar sign ($), question mark (?), or underline (_).
The first 64 characters are used by the assembler sizesymbol control may reduce the number).
Symbols that start with a dollar sign are local symbols and are only defined in a local region. (see the .local directive)
Symbols are case sensitive.
Symbols and labels are used to provide a convenient name for values and addresses. The rules for constructing symbol names and the rules for constructing label names are the same; only use distinguishes a symbol from a label. the Section called label field describes how values are assigned to labels. Chapter 5 and the .set syntax documentation describe how values are assigned to symbols.