GATE 2015 COMPUTER SCIENCE & INFORMATION TECH. – CS – C Programming | Q. 62 (Shift – 1)

October 1, 2026October 1, 2026 Gopal Krishna 19 Views 0 Comments 2-D Arrays in C, Array and Pointer, C Array Indexing, C Pointers, C programming, Dereference Operator, GATE 2015, GATE C Programming, GATE Computer Science, GATE CS, GATE Questions, Memory Address in C, Multidimensional Arrays, Pointer Arithmetic

📌 GATE 2015 – Question 62

Question Type: MCQ

What is the output of the following C code? Assume that the address of x is 2000 (in decimal) and an integer requires four bytes of memory.

int main()
{
    unsigned int x[4][3] =
        {
            {1, 2, 3},
            {4, 5, 6},
            {7, 8, 9},
            {10, 11, 12}
        };

    printf("%u, %u, %u", x+3, *(x+3), *(x+2)+3);
}

Options:

(A) 2036, 2036, 2036 (B) 2012, 4, 2204

(C) 2036, 10, 10 (D) 2012, 4, 6

Solution

🔹 Understanding the 2-D Array

The declaration in the question is:

    unsigned int x[4][3];
  

Therefore, x is a 2-D array with 4 rows and 3 columns. It contains a total of 4 × 3 = 12 elements.

The values given in the question are arranged as follows:

Index	Column 0	Column 1	Column 2
Row 0	x[0][0] = 1	x[0][1] = 2	x[0][2] = 3
Row 1	x[1][0] = 4	x[1][1] = 5	x[1][2] = 6
Row 2	x[2][0] = 7	x[2][1] = 8	x[2][2] = 9
Row 3	x[3][0] = 10	x[3][1] = 11	x[3][2] = 12

📌 Important: In x[i][j], the first index i represents the row, while the second index j represents the column. Note that for computer 0 is also a number and numbering starts from 0. Humans generally start counting from 1. So, rwo and column numbering starts from 0.

For example: x[2][2] = 9 means row 2, column 2 contains the value 9.

🔹 Arrays and Pointers Are Closely Related

Before solving the 2-D array question, let us first understand the relationship between an array and a pointer using a simple 1-D array.

    int a[3] = {10, 20, 30};
  

This array contains 3 elements. Remember that array indexing starts from 0.

Index	Element	Value	Pointer Expression
0	a[0]	10	a or (a + 0) = &a[0]
1	a[1]	20	(a + 1) = &a[1]
2	a[2]	30	(a + 2) = &a[2]

📌 Key Idea: When the array name a is used in an expression, it represents a pointer to the first element, a[0]. &a[0] represents address of element a[0]. Here & is the ‘address of operator’. Like every operator returns a value, & returns address or pointer or memory location of an element that it is used with.

Therefore:

    a + 0  →  points to a[0]  →  value 10

    a + 1  →  points to a[1]  →  value 20

    a + 2  →  points to a[2]  →  value 30

To obtain the value stored at these locations, we use the dereference operator (*):

    *(a + 0) = a[0] = 10

    *(a + 1) = a[1] = 20

    *(a + 2) = a[2] = 30

💡 Remember: a[0], a[1], and a[2] are the three elements of the array. The numbers inside the square brackets are called indices, and indexing starts from 0.

🔹 Pointer Representation of a 2-D Array

Now let us apply the same idea to the 2-D array used in this question:

    unsigned int x[4][3]
  

This array has 4 rows and 3 columns. In a 2-D array, the array name x, when used in an expression, represents a pointer to the first row.

📌 Key Difference: In a 1-D array, pointer arithmetic moves from one element to the next. In this 2-D array, x + 1 moves from one row to the next row.

Row	Array Row	Pointer Expression	Points To
Row 0	x[0]	x or x + 0	Row 0
Row 1	x[1]	x + 1	Row 1
Row 2	x[2]	x + 2	Row 2
Row 3	x[3]	x + 3	Row 3

The four rows of the array are:

    x[0] = {1, 2, 3}

    x[1] = {4, 5, 6}

    x[2] = {7, 8, 9}

    x[3] = {10, 11, 12}

💡 Therefore:
x → points to Row 0
x + 1 → points to Row 1
x + 2 → points to Row 2
x + 3 → points to Row 3

📌 Important: The expression x + 1 does not point to the next individual element such as x[0][1]. It points to the next complete row, because each element of x is itself a row containing 3 unsigned int elements.

🔹 Memory Addresses of the 2-D Array Elements

The question states that the address of x is 2000 (in decimal), and each unsigned int requires 4 bytes of memory.

📌 Important: The elements of a 2-D array are stored in contiguous memory locations, row by row. Therefore, the address increases by 4 bytes from one integer element to the next.

Element Address	Address (Decimal)
&x[0][0]	2000
&x[0][1]	2004
&x[0][2]	2008
&x[1][0]	2012
&x[1][1]	2016
&x[1][2]	2020
&x[2][0]	2024
&x[2][1]	2028
&x[2][2]	2032
&x[3][0]	2036
&x[3][1]	2040
&x[3][2]	2044

💡 Observe the pattern:
2000 → 2004 → 2008 → 2012 → 2016 → … → 2044

Each successive unsigned int occupies the next 4 bytes of memory.

🔹 Finding the Value of (x + 3)

We have already seen that x is a 2-D array with 4 rows and 3 columns. In a 2-D array, pointer arithmetic with the array name x moves row by row.

    x + 0  →  Row 0

    x + 1  →  Row 1

    x + 2  →  Row 2

    x + 3  →  Row 3

📌 Therefore:
x + 3 points to Row 3 of the 2-D array.

Row 3 contains three elements:

Element	Value	Address
x[3][0]	10	2036
x[3][1]	11	2040
x[3][2]	12	2044

Since x + 3 points to the beginning of Row 3, it points to the address where Row 3 starts.

    x + 3 = &x[3]
    
    &x[3] = &x[3][0]
    
    &x[3][0] = 2036

💡 Important Point:
Although Row 3 contains three elements at addresses 2036, 2040, and 2044, the expression x + 3 points to the start of Row 3. Therefore, its address is 2036.

📌 Conclusion:
x + 3 = 2036

Next: We will now understand what happens when we apply the * (dereference) operator to (x + 3).

🔹 Understanding *(x + 3)

We have already established that x + 3 points to Row 3 of the 2-D array.

    x + 3
    → points to Row 3
    
    x + 3 = &x[3]
    
    &x[3] = &x[3][0] = 2036

Now we apply the dereference operator (*):

    *(x + 3) = x[3]
  

Row 3 contains three elements:

Element	Value	Address
x[3][0]	10	2036
x[3][1]	11	2040
x[3][2]	12	2044

📌 What does x[3] represent?
x[3] represents the entire fourth row: {10, 11, 12}.

But there is one more important point. Since x[3] is an array, when it is used in an expression, it is converted to a pointer to its first element.

    x[3]
    
    ↓
    
    &x[3][0]
    
    ↓
    
    Address = 2036

💡 Therefore:

*(x + 3) = x[3]

x[3] is the fourth row {10, 11, 12}. When this array is used as a value in an expression, it refers to the address of its first element, x[3][0].

Therefore: *(x + 3) = 2036

📌 In one line:
x + 3 → Row 3 → *(x + 3) → x[3] → &x[3][0] → 2036

🔹 An Important Point About *(x + 3)

The expression we are evaluating in the question is:

    *(x + 3)
  

We already know that:

    x + 3 → points to Row 3
    
    *(x + 3) → gives Row 3

Row 3 is:

    x[3] = {10, 11, 12}
  

📌 What does “used in an expression” mean?

The array x[3] can be converted to a pointer to its first element when it is used in a context where a pointer is required. In that case:

x[3] → &x[3][0]
&x[3][0] = 2036

💡 Important:
We should not immediately say that *(x + 3) is 2036. The exact type and context of the expression must be considered.

Next: We will examine the type of x, x + 3, and *(x + 3) step by step. This will tell us exactly what happens in the printf() statement.

🔹 Understanding *(x + 2) + 3

Let us evaluate the expression step by step:

    *(x + 2) + 3
  

Step 1: Find x + 2

In the 2-D array, x points to Row 0. Therefore:

x + 2 → Row 2

Row 2 contains: {7, 8, 9}

Step 2: Apply the * operator

*(x + 2) = x[2]

Therefore, *(x + 2) represents Row 2:
x[2] = {7, 8, 9}

Step 3: What happens when we add 3?

Here we have:

x[2] + 3

Since x[2] is an array, in this expression it is converted to a pointer to its first element:

x[2] → &x[2][0]

Element	Value	Address
x[2][0]	7	2024
x[2][1]	8	2028
x[2][2]	9	2032

Step 4: Move 3 integer positions

The pointer starts at &x[2][0], whose address is 2024.

Each unsigned int occupies 4 bytes. Therefore, moving 3 positions means:

3 × 4 = 12 bytes

Hence:

2024 + 12 = 2036

💡 Therefore:

*(x + 2) + 3
= x[2] + 3
= &x[2][0] + 3
= 2024 + (3 × 4)
= 2036

📌 Key point: The + 3 here is pointer arithmetic. It moves three unsigned int positions from the beginning of Row 2. It does not mean adding the number 3 to the value 7.

✅ Final Answer

From the above calculations:

    x + 3 = 2036
    
    *(x + 2) + 3 = 2036

Therefore, the required output of the given printf() expression is:

    2036, 2036, 2036
  

🎯 Correct Option:

(A) 2036, 2036, 2036

GATE_2015_Q62_Important_Relations Download

Gopal Krishna

You May Also Like

Leave a Reply Cancel reply