Question

Explain 3 Register addressing modes?

Answer 1

Background:
Normally,an instruction is a group of three components.

a)Operation Code(Opcode):specifies which operation is to be performed.
b)Address/Operand:Operation is performed upon a quantity.this quantity is called operand.
instead of having operand,there may be address of operand in some cases
c)Addressing Mode:this is a way of specifying operand of an instruction.

Ans
Register Mode:
in this adressing scheme(register addressing), operand is stored in a general purpose register.instruction specifies a register and this register contains operand.

Register Indirect mode:
in this case,instruction specifies a register and this register contains the effective address of operand(operand is placed in memory).

Base register addressing mode:
in this addressing scheme, the effective address is obtained by adding the value of base register to the value of address field

Auto Indexed (increment mode):instruction specifies a register and this register contains the effective address of operand.the content of this register(address of operand) is automatically incremented after accessing operand.now it can point to the next consecutive memory location.

Auto indexed ( Decrement mode):
instruction specifies a register and this register contains the effective address of operand.the content of this register(address of operand) is automatically decremented before accessing operand.now it can point to the previous consecutive memory location.