Addressing mode

Question

I'm studying for an exam called Computer Fundamental, and started taking some previous exam but the given documents i had is way inadequate to solve all the question mentioned, like this one :

Which of the following is the correct combination of variousaddressing modes? Here, X1 is an address which is stored in a program counter. X2is an address part of an instruction which is addressed by X1.X3is an address in which an operand needed to execute an instruction is stored. X4is a value in an index register. (X2) means the contents of location X2.

I tried to google "Addressing mode" and came up with some resources that i can't understand.

Can someone recommend me some link where i can get to know more about addressing mode so that i can answer this question?

Thanks alot!

I'm sorry for the tag, can't find some thing like "address" or "addressing mode"

Answer 1

I recommend you start by understanding what "direct addressing", "indirect addressing", "PC-relative addressing", and "indexed addressing" mean. With any luck, your textbook will explain those. If not, you should be able to find many explanations on the Internet. At last resort, check out the manual for your favorite processor.

Answer 2

The correct answer is b.

1.In direct addressing mode the effective address is equal to the address part of instruction so X3 = X2.

2.In indirect addressing mode the effective address is equal to the content of the address part of instruction so X3 = (X2).

3.In relative addressing mode the effective address is equal to the sum of the address part of instruction and the content of program counter so X3 = X1 + X2.

3.In indexed addressing mode the effective address is equal to the sum of the address part of instruction and the content of index register so X3 = X2 + X4.

If you wanna read more about addressing mode then refer this http://www.cs.iit.edu/~cs561/cs350/addressing/addsclm.html