The syntax of the expression evaluate operator (%) is

     %expression

The expression is evaluated and its value is used to replace the expression itself. Typically, this operator is used to provide an argument in a macro call.

Example: Consider a macro to allocate and initialize an array of a given size. Assume that the macro receives the array name and size, element size (B for byte, W for word, ...), and the initial value.

init_array MACRO element_size, name, size, init_value

name D&element_size size DUP (init_value)

ENDM

To reserve space for an integer array of 47x7 (marks) and initialize it to -1, we can call the macro as:

     init_array W, marks, %47*7, -1

The macro call will be expanded as

     marks  DW  329 DUP (-1)