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What will be the output of the following C code?

#include <stdio.h>
    void main()
    {
        int a = -5;
        int k = (a++, ++a);
        printf("%d\n", k);
    }

 

  • A.-3
  • B.-5
  • C.4
  • D.Undefined

Answer: A

Correct answer: -3

The comma operator evaluates its left operand, discards the result, then evaluates the right and yields that value.

So a++ runs first, taking a from −5 to −4 and yielding −5, which is thrown away. Then ++a takes a to −3 and yields −3, which is assigned to k. The comma also introduces a sequence point, so the two modifications of a are properly ordered and the behaviour is defined.

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