ISRO CS 2023 Q.27: solution and answer

ISRO 2023 · CSQ.27 · 1 mark · MCQ

Pointer p to an array of integers (of size 2 Bytes) is initialised to 200. What is the value of p+3?

See the question in the paper

Answer and solution

ANSWER

$p + 3 = 206$ , which is option (A).

Pointer arithmetic scales by the size of the pointed-to type: $p + n$ moves the address by $n \times sizeof (* p)$ bytes.
Each integer element occupies $2$ bytes and $p = 200$ .
So $p + 3 = 200 + 3 \times 2 = 206$ .
Option (b) $203$ adds $3$ bytes and ignores the scaling. Option (c) $212$ would need a $4$ -byte element, since $200 + 3 \times 4 = 212$ . Option (d) $204$ equals $p + 2$ , which is an off-by-one in the element count.

KEY IDEA

Adding $n$ to a pointer advances it by $n$ elements, so the address changes by $n \times sizeof$ (element type) bytes.

WATCH OUT FOR

Adding $3$ to the address directly, which gives $203$ . This forgets that pointer arithmetic is scaled by the element size.