直接和隐式寻址模式之间的差异

先决条件–寻址模式

1.直接寻址模式：
在直接寻址模式下，地址字段包含操作数的地址。

Effective Address(EA) = address field of operand 

例子 –
将寄存器A的内容添加到累加器。

ADD A 

在地址A的内存中查找操作数。只需一个内存引用即可访问数据。因此，无需其他计算即可得出有效地址。

2.隐式寻址模式：
在指令的定义中隐式指定了操作数。通常用于零地址或单地址指令。

示例1：
递增寄存器A的内容。

INC A 

此处隐式指定了寄存器A既是源，也是目的地。

示例2：
清除标志寄存器的内容。

CLC 

上面的指令是零地址指令的示例。

直接和隐式寻址模式之间的区别：

DIRECT ADDRESSING MODE	IMPLIED ADDRESSING MODE
Address fields contains the effective address of operand.	Effective address of operand is specified implicitly.
Instruction size is larger since operand has to be explicitly specified.	Instruction size is smaller since operand is specified implicitly.
It requires one reference to memory.	No memory references are required.
Mostly used in 2 address instructions and more.	Mostly used in zero address and single address instructions.
It is slower compared to implied mode.	It is a faster method.
It has more range than implied mode.	It has less range than direct mode.