Consider the C struct defined below: struct data int marks [100]; char grade; 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.

Official answer: D) Index addressing mode, X(R1), where X is an offset represented in 2's complement 16-bit representation.. Explanation: To access a specific field within a structure: 1. The base address of the structure variable `student` is fixed in register `R1`. 2. The member `grade` is located at a fixed compile-time byte offset from the start of the structure (specifically, the offset is after `marks[100]`, which is 100 sizeof(int) bytes, plus any required padding/alignment). 3. In assembly/machine language, accessing an element at a fixed displacement from a base register is most efficiently performed using Base-Register / Indexed / Displacement addressing mode: Effective Address = Base Register (R1) + Offset X where X is the constant offset. Therefore, (D) is the correct option.

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 and Architecture · Instruction Set and Addressing Modes

Official IIT answer key · IIT Roorkee · Audited Aug 2026

Take topic test

GATE CSE 2017 Set 1 Q11 · MCQ · 1 mark

Consider the C struct defined below: `struct data { int marks [100]; char grade; int cnumber; }; struct data student;` The base address of `student` is available in register R1. The field `student.grade` can be accessed efficiently using

Select an option to check

Key concept

Instruction Set and Addressing Modes

Step-by-step verified solution

Examiner trap & misconception

Topic notes

How GATE tests Instruction Set and Addressing Modes

Instruction set and addressing modes in GATE CS is consistently tested through instruction word encoding, expanding opcode schemes, addressing mode semantics, and ISA architectural principles. Problems evaluate a candidate's ability to calculate bit allocations for opcodes, register specifiers, and immediates, as well as mapping high-level constructs (structs, arrays, pointers) to assembly addressing modes. The topic features a healthy mix of conceptual 1-mark MCQs/MSQs and rigorous 2-mark NATs involving bit calculations and assembly program traces.

Full Instruction Set and Addressing Modes guide →

More on Instruction Set and Addressing Modes

All 19 questions on Instruction Set and Addressing Modes →

Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.

Computer Organization and Architecture · Instruction Set and Addressing Modes

Official IIT answer key · IIT Roorkee · Audited Aug 2026

Take topic test

GATE CSE 2017 Set 1 Q11 · MCQ · 1 mark

Consider the C struct defined below: `struct data { int marks [100]; char grade; int cnumber; }; struct data student;` The base address of `student` is available in register R1. The field `student.grade` can be accessed efficiently using

Select an option to check

Key concept

Instruction Set and Addressing Modes

Step-by-step verified solution

Examiner trap & misconception

Topic notes

How GATE tests Instruction Set and Addressing Modes

Full Instruction Set and Addressing Modes guide →

More on Instruction Set and Addressing Modes

All 19 questions on Instruction Set and Addressing Modes →

Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.

Consider the C struct defined below: `struct data { int marks [100]; char grade; int cnumber; }; struct data student;` The base address of `student` is available in register R1. The field `student.grade` can be accessed efficiently using

Step-by-step verified solution

Check you can still solve Instruction Set and Addressing Modes under a clock

More from GATE CSE 2017 Set 1

More on Instruction Set and Addressing Modes

Consider the C struct defined below: `struct data { int marks [100]; char grade; int cnumber; }; struct data student;` The base address of `student` is available in register R1. The field `student.grade` can be accessed efficiently using

Step-by-step verified solution

Check you can still solve Instruction Set and Addressing Modes under a clock

More from GATE CSE 2017 Set 1

More on Instruction Set and Addressing Modes

Consider the C struct defined below: struct data { int marks [100]; char grade; int cnumber; }; struct data student; The base address of student is available in register R1. The field student.grade can be accessed efficiently using

Step-by-step verified solution

Check you can still solve Instruction Set and Addressing Modes under a clock

More from GATE CSE 2017 Set 1

More on Instruction Set and Addressing Modes

Share this solution

Consider the C struct defined below: struct data { int marks [100]; char grade; int cnumber; }; struct data student; The base address of student is available in register R1. The field student.grade can be accessed efficiently using

Step-by-step verified solution

Check you can still solve Instruction Set and Addressing Modes under a clock

More from GATE CSE 2017 Set 1

More on Instruction Set and Addressing Modes

Share this solution

Consider the C struct defined below: `struct data { int marks [100]; char grade; int cnumber; }; struct data student;` The base address of `student` is available in register R1. The field `student.grade` can be accessed efficiently using

Consider the C struct defined below: `struct data { int marks [100]; char grade; int cnumber; }; struct data student;` The base address of `student` is available in register R1. The field `student.grade` can be accessed efficiently using