GATE CSE 2015 Set 1 | Question: 35

Question

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); 
}

• A. $2036, 2036, 2036$
• B. $2012, 4, 2204$
• C. $2036, 10, 10$
• D. $2012, 4, 6$

Comments

some source or material to read about this, quickly?

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For better explanation refer the below link:

 

https://www.google.com/amp/s/www.geeksforgeeks.org/pointer-array-array-pointer/amp/

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www.cs.cmu.edu%2F~ab%2F15-123S09%2Flectures%2FLecture%252006%2520-%2520%2520Pointer%2520to%2520a%2520pointer.pdf

Check : Accessing 2D arrays using pointers

Answer 1

Explanation supporting *(x+3) = 2036

• int A[m][n];
• We can think of A[0] as the address of row 0, A[1] as the address of row 1  
• In general: A[i][j] = *(A[i] + j) = *(*(A+i)+j)
• Example: A[0][2] = *(A[0] + 2)
 
  o Note that: A[0] = *A
• Hence, if A is a 2D int array, we can think of A as a pointer to a pointer to an integer. That is, int**

Hence *(x+3) would return 2036.

Comments

Please explain how x+3 = *(x+3) ???

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x is a 2D array, it decays to a 2D pointer. So x + 3 with one level of indirection is equivalent to *(x + 3).

Answer 2

This image may help to visualise, sorry for bad lighting 

Pro trick :- To access 1 dimensional array element need one * asterisk

 

For 2d - ** two asterisk

For 3d -- *** three asterisk