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I am watching IIT Madras lecture of Addressing mode, in that Prof take an example, in which we have a register r0 = 1000

Link:- https://www.youtube.com/watch?v=p9wxyIx-j-c&index=12&list=PLQObLunIEgaQ7Drxp8yCmsJqidgSsTqlw

Time :- 05:10

Content of Memory location 1000 = 1010

Content of Memory location 1010 = DATA

According to his definition, he described 3 addressing modes 

Register mode: Data is present in the register. 

Register Direct mode : In this the ADDRESS OF THE DATA IS DIRECTLY PRESENT IN THE REGISTER.

Register Indirect mode/ Register Deferred mode: In this register contain the address 1000, and the content of M[1000] is 1010 which is also a address, content of m[1010] is ACTUAL DATA.

Which means in

Register mode to get the data 1 Reg Ref is required.

Register Direct mode to get the data 1 Reg Ref and 1 Mem ref is required.

Register Indirect Mode to get the data 1 Reg Ref and 2 Mem ref is required.

But In CARL HAMACHER:-

Register Indirect is defined through this diagram:-

while according to IIT Madras Prof it should be Register DIrect mode.

which one among these are true or something I am missing.

in CO and Architecture by Boss (18.1k points)
retagged by | 991 views

1 Answer

0 votes

whatever that teacher said in the lecture is not correct. find the following definition from Moris Mano's book

Instruction contains the register name and the reguster contains the address of operand. 

by Boss (43.1k points)
0

Ok so, carl Hamacher and Morris Mano both are conveying the same concept but Prof. did mistake.

This one is Register or Register Direct mode

ADD R0 R1

 and This one is Register Indirect mode

ADD R0 M[R1]

And below one what type:-

ADD R0 M[M[r1]]

 is it of REGISTER DOUBLE INDIRECT.

0
There is no where mentioned such Register Double indirect, in fact there is no use of such addressing mode, why will someone access memory twice for no reasons.
0
we have solved many question on pointer to pointer in programming and data structure based on double indirect addressing mode only.
0

Yes! for that purpose we have "Memory Indirect Addressing Mode", 

But why will someone have Double Register Indirect addressing mode? 

for indirect access, either a memory location or a register can be used.

+1
Actually not only double but triple and further more addressing mode exist but they are not in practice because they use memory cycle and waste of time.

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