A single ampersand indicates the presence of a variable symbol. The assembler substitutes the value of the variable symbol into the character string specified in a macro instruction operand. The resultant string is then the value passed into the macro definition. If the variable symbol is undefined, an error message is issued.

Double ampersands must be specified if a single ampersand is to be passed to the macro definition.

&VAR
&A+&B+3+&C*10
'&MESSAGE'
&&REGISTER