GATE CS 2024 Set 2 Q26 — Programming in C

Let us trace the execution of the program step-by-step:

1. Array Initialization:

   An array a of two double elements is initialized as:

   a[0] = 20.0 and a[1] = 25.0

2. Pointer Assignments:
   • p = a; makes p point to the first element a[0].
   • q = p + 1; makes q point to the next element a[1].
3. Evaluating the Expressions in printf:
   • First Expression (int)(q - p):
     In C, pointer subtraction (q - p) yields the distance between the two pointers in terms of the number of elements of the base type (here, double), not the number of bytes. Since q points to index 1 and p points to index 0: $$\text{q} - \text{p} = 1$$ Casting this to int gives 1.
   • Second Expression (int)(*q - *p):
     Dereferencing the pointers gives their respective values: $$*\text{q} = 25.0 \quad \text{and} \quad *\text{p} = 20.0$$ Subtracting these values: $$*\text{q} - *\text{p} = 25.0 - 20.0 = 5.0$$ Casting 5.0 to int gives 5.

Thus, the printf statement outputs 1,5, which corresponds to option B.