Differences among 10 addressing modes

1. Implicit addressing ： The address of the operand is implied in the instruction . Hardware that can shorten the instruction word length but needs to increase the storage operand or implied address .

2. Address immediately ： The address field of the instruction is the operand itself . No need to access main memory , Short execution time , But its number of digits limits the range of immediate numbers .

3. Direct addressing ： Formal address A Is the real address of the operand . Simple , But the address of the operand is not easy to modify .

4. Introduction addressing ： The address of the instruction is the address of the storage unit where the effective address of the operand is located . The addressing range can be expanded , But access is slow .

5. Register addressing ： The instruction directly gives the register number where the operand is located . Fast execution , But the number of registers is limited .

6. Register indirection ： The Register gives the address of the main memory unit where the operand is located . Faster than general indirect addressing , But it needs to access main memory .

7. Relative addressing ： hold PC Add the formal address in the instruction format to form the effective address of the operand . The address of the operand is not fixed , There is a fixed difference between and the instruction , Convenient for program floating .

8. Base addressing ： take CPU The contents of the base register in plus the formal address in the instruction format form the effective address of the operand . It is operating system oriented , The addressing range can be expanded , It is conducive to the realization of multiprogramming , But the number of bits offset is less .

9. Addressing ： The sum of the formal address in the instruction word and the content in the index register . User oriented , Expand the addressing range .

10. Stack addressing ： Follow the principle of last in first out .

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