Difference between 3-address instruction and 1-address instruction

Prerequisite – Instruction Formats
1. Three-Address Instructions:
Three-address instruction is a format of machine instruction. It has one opcode and three address fields.

2. One-Address Instructions:
One-Address instruction is also a format. It has only two fields. One for opcode and other for operand.

Difference between Three-Address Instruction and One-Address Instruction:



Three-Address Instruction One-Address Instruction
It has four fields. It has only two fields.
It has one field for opcode and three fields for address. It also has one field for opcode but there is only one field for address.
It has long instruction length. It has shorter instruction.
There may be three memory accesses needed for an instruction. There is a single memory access needed for an instruction.
It is slower accessing location inside processor than memory. It is faster accessing location inside processor than memory.
It disadvantage i.e. three memory access is eliminated by two-address memory. It eliminated two memory access.
There are three location for operand and result. There is only one location for operand and result.

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