One Address Instructions

One address instructions specify one operand or address, where the address usually refers to either a memory location or a register.  One address instruction uses an implied ACCUMULATOR register for data manipulation. One operand is stored in the accumulator, while the other is in a register or memory location.

Note: Implied means that the CPU already knows that one operand exists in the accumulator register and there is no need to specify it.

Advantages of single address instructions

Let’s see some advantages of one-address instructions

  • One of the operands is always held in the accumulator register, resulting in shorter instructions and less memory usage.
  • Less time is required to complete the Instruction cycle.

Disadvantages of single address instructions

Let’s see some disadvantages of one-address instructions
  • When executing complex expressions, the program size increases due to many small single-address instructions.
  • As the number of instructions in a program increases, the time taken for its execution also increases.

Examples of One Address Instructions

In this section, we will see various examples of one address instructions in detail.

Example 01:

Write a program for one address instructions to evaluate the following arithmetic instruction