Three-Address Code: Operand Count and Meaning

In compiler design, three-address code is a form of intermediate code in which each instruction is represented using three addresses (fields that denote locations/identifiers). A typical instruction has the form:
$\text{(result)} \;=\; \text{(arg1)} \;\text{op}\; \text{(arg2)}$
So, a three-address statement conceptually uses three operand “addresses”: the two operands (arg1, arg2) and the destination/result address.

A standard contrast is:

• one-address code: fewer explicit address fields.
• two-address code: two fields (e.g., $x = x \;+\; y$ style).
• three-address code: separates operands from destination.

Therefore, for the multiple-choice question:

A three-address code uses (iii) Three operands.

However: note the wording “operands” can be ambiguous—some textbooks say “three addresses/fields,” while others say “operands including destination.” In either interpretation, three-address code corresponds to the choice that includes three operand/address fields (two sources + one destination).

Expected answer: (iii) Three operands.

Key idea: “three addresses” = arg1, arg2, and result

A three-address instruction explicitly names:

1. the first operand address (arg1),
2. the second operand address (arg2),
3. the result/destination address (result).

This is why three-address code is often written like:

• $t1 = a + b$
• $t2 = t1 * c$

Here, each line has two source operands and one destination temporary—three address fields total. three-address code temporary variable intermediate representation