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What will be the output of the following C code?

#include <stdio.h>
    void main()
    {
        int x = 4;
        int *p = &x;
        int *k = p++;
        int r = p - k;
        printf("%d", r);
    }

 

  • A.4
  • B.8
  • C.1
  • D.Run time error

Answer: C

Correct answer: 1

Pointer arithmetic is in units of the pointed-to type, not in bytes. p++ advances p by one int, and k keeps the address p held beforehand, since ++ is postfix.

The difference of two pointers is likewise expressed in elements:

\[ p - k = 1 \]

The distractor 4 is the difference in bytes on a machine with four-byte ints, which is what a beginner expects; the language deliberately hides that scaling so that pointer arithmetic works the same way for every type.

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