该指令系统包含三地址指令、双地址指令、单地址指令和零地址指令 指令长度为16位，包括4位基本操作码字段和三个4位地址字段 根据给定的各类指令的条数，设计出合理的扩展操作码方案-The instruction system includes a three-address instruction, two-address instruction, single-address instruction and zero-address instruction length of 16 ins