Question 1

Consider the C struct defined below:

```    struct data   {
int marks [100];
int cnumber;
};
struct data student;
```

The base address of student is available in register R1. The field student.grade can be accessed efficiently using

 A Post-increment addressing mode, (R1)+ B Pre-decrement addressing mode, -(R1) C Register direct addressing mode, R1 D Index addressing mode, X(R1), where X is an offset represented in 2’s complement 16-bit representation
Computer-Organization       Addressing-Modes       GATE 2017 [Set-1]       Video-Explanation
Question 1 Explanation:
sruct data
{
int marks[100];
int cnumber;
}; struct data student
Base Address of student is available in R1.
It is clearly mentioned X is the offset address to be summed with Base Address of R1.

Hence Index Addressing mode X(R1), where X is an offset represented in 2’s complement 16-bit representation.
⇾ Relative, Base Indexed & all subtypes of Indirect addressing modes are used with Arrays.
 Question 2

Which of the following is/are true of the auto-increment addressing mode?

I. It is useful in creating self-relocating code
II. If it is included in an Instruction Set Architecture, then an additional ALU is required for effective address calculation
III. The amount of increment depends on the size of the data item accessed
 A I only B II only C III Only D II and III only
Question 2 Explanation:
I. Self relocating code always takes some address in memory. So auto-increment mode is not used for self relocating code. Hence this statement is wrong.
II. An additional ALU is not necessary for auto-increment. So this statement is wrong.
III. In auto-increment addressing mode the address where next data block to be stored is generated automatically depending upon the size of single data item required to store. This is based on pointer arithmetic. So this statement is true.
Hence option C is the answer.
 Question 3

Which of the following addressing modes are suitable for program relocation at run time?

```(i)  Absolute addressing     (ii) Based addressing
 A (i) and (iv) B (i) and (ii) C (ii) and (iii) D (i), (ii) and (iv)
Question 3 Explanation:
A fixed address in memory which indicates a location by specifying a distance from another location. In this displacement type addressing is preferred.
So, option A is false.
This scheme is used by computers to control access to memory. In this pointers are replaced by protected objects which can be executed by kernel (or) some other privileged process authors.
So, this is suitable for program relocation at runtime.
The offset of the relative addressing is to allow reference to code both before and after the instruction.
This is also suitable.
Which leads to extra memory location which can be not suitable at run time.
This is not suitable.
 Question 4

 A the operand is inside the instruction B the address of the operand is inside the instruction C the register containing the address of the operand is specified inside the instruction D the location of the operand is implicit
Question 4 Explanation:
The operand is inside the instruction---Immediate addressing.
The operand is inside the instruction --- absolute addressing.
The register containing the address of the operand is specified inside the instruction --- Register addressing.
The location of the operand is implicit --- Implicit addressing.
 Question 5

A certain processor supports only the immediate and the direct addressing modes. Which of the following programming language features cannot be implemented on this processor?

 A Pointers B Arrays C Records D Recursive procedures with local variable E All the above
Question 5 Explanation:
A) Cannot be implemented because pointers need indirect addressing mode.
B) Cannot be implemented because arrays need Register indexing.
C) Records also needs pointers which needs indirect addressing modes, so this also cannot be implemented.
D) Recursive procedures needs stack, and so it needs stack pointers which in turn needs indirect addressing. So this also cannot be implemented.
 Question 6

Which of the following addressing modes permits relocation without any change whatsoever in the code?

Question 6 Explanation:
In PC relative addressing there is no change in the code.
 Question 7

Relative mode of addressing is most relevant to writing

 A coroutines B position – independent code C shareable code D interrupt handlers
Question 7 Explanation:
The main advantage of PC- relative addressing is that code may be position independent, i.e., it can be loaded anywhere in memory without the need to adjust any address.
 Question 8

The instruction format of a CPU is:

Mode and RegR together specify the operand. RegR specifies a CPU register and Mode specifies an addressing mode. In particular, Mode = 2 specifies that ‘the register RegR contains the address of the operand, after fetching the operand, the contents of RegR are incremented by 1’.

An instruction at memory location 2000 specifies Mode = 2 and the RegR refers to program counter (PC).
(a) What is the address of the operand?
(b) Assuming that this is a non-jump instruction, what are the contents of PC after the execution of this instruction?

 A Theory Explanation.
 Question 9

The most relevant addressing mode to write position-independent codes is:

 A Direct mode B Indirect mode C Relative mode D Indexed mode
Question 9 Explanation:
Relative mode since we can just change the content of base register, if we wish to relocate.
 Question 10

 A It enables reduced instruction size B It allows indexing of array elements with same instruction C It enables easy relocation of data D It enables faster address calculations than absolute addressing
Question 10 Explanation:
 Question 11
The most appropriate matching for the following pairs :
 A X − 3, Y − 2, Z −1 B X − 2, Y − 3, Z −1 C X − 3, Y −1, Z − 2 D X − 2, Y −1, Z − 3
Question 11 Explanation:
Indirect addressing means that the address of the data is held in an intermediate location so that the address is first 'looked up' and then used to locate the data itself.
Immediate Addressing. An immediate operand has a constant value or an expression. When an instruction with two operands uses immediate addressing, the first operand may be a register or memory location, and the second operand is an immediate constant. Auto increment or decrements: can be one by using loops.
 Question 12
Relative mode of addressing is most relevant to writing
 A Coroutines B Position-independent code C Shareable code D Interrupt Handlers