a. A 2-pass assembler can handle future symbols and an instruction can therefore use a future symbol as an operand. This is not always true for directives. The EQU directive, for example, cannot use a future symbol. The directive 'A EQU B+1' is easy to execute if B is previously defined, but impossible if B is a future symbol. What's the reason for this?
b. Suggest a way for the assembler to eliminate this limitation such that any source line could use future symbols.