GATE CSE 1989 | Question: 2-ii

Question

Match the pairs in the following questions:$$\begin{array}{ll|ll}\hline \text{(A)} & \text{Base addressing} & \text{(p)} & \text{Reentranecy} \\\hline  \text{(B)} & \text{Indexed addressing} & \text{(q)}& \text{Accumulator} \\\hline   \text{(C)}& \text{Stack addressing} & \text{(r)}  & \text{Array} \\\hline  \text{(D)} & \text{Implied addressing} &\text{(s)}  & \text{Position independent}  \\\hline \end{array}$$

Answer 1

$$\begin{array}{ll|ll}\hline \text{(A)} & \text{Base addressing} & \text{(s)} & \text{Position independent (By changing the value in}\\ &&& \text{base register, location of address can be changed)} \\\hline  \text{(B)} & \text{Indexed addressing} & \text{(r)}& \text{Array} \\\hline   \text{(C)}& \text{Stack addressing} & \text{(p)}  & \text{Reentranecy (Whenever code happens to be used}\\ &&& \text{again, address need not be the same)} \\\hline  \text{(D)} & \text{Implied addressing} &\text{(q)}  & \text{Accumulator (If an address is not specified, it is}\\ &&& \text{assumed/implied to be the Accumulator)}  \\\hline \end{array}$$

Comments

How C-Accumulator and D-Reentrancy related?

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Yes i missed . Implicit/ implied has no address so have default regirtser called Accumalator on which computation done.

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can you elaborate "reentrancy" a bit ?

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@Bhavana Usually all function variables are stored on its activation record. Now, if this function is called multiple times, the activation record cannot always have the same address -- especially in case of recursion. To handle this, we store the start address of activation record in a register called Stack Pointer and now each invocation of a function gets its own memory space for activation record but uses same offsets for all their variables -- by using stack addressing.

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@Arjun Sir, we need to store start address of every activation record?

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That gets stored as part of the function call.

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So we are relating stack addressing to reentrancy because the same function when called multiple times it re-enter into the stack multiple time.

ryt?

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But base addressing is not position independent as the address stored by base register depends on the memory it is loaded to,then how can we say that!?

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@prachi gupta Base AM is position independent AM because it is used to access the data element presents in the different segments of memory system

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@Arjun sir, please explain

but uses same offsets for all their variables

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Offsets can be understood as a displacement from the start address. Now considering the multiple recursion case for a single program, Now every activation record will have different starting address but the displacement of the variables will be the same.

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@Arjun is reentrancy same as displays [ ].....???? Which stores the Addresses of the each activation record...

Answer 2

Base Addressing → Position independent addressing
Indexed Addressing → Array [In indexed addressing updation of micro instruction is a costly]
Stack Addressing → Reentrancy
 Implied Addressing → Accumator and other SPR (sometimes GPRs as well)

Answer 3

A-S,  B-R, C-P, D-Q

Comments

Hows A-Q?

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Base addressing points the Base address of the program . . . And offset will be added for the absolute address . . So I thought accumulator will be apt

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No, whenever we don't say an address, Accumulator is implied. So, D-Q.