Discussion

What is the output of this C code?

 int main()
    {
        int x = 2;
        x = x << 1;
        printf("%d\n", x);
    }

Answer: A

Correct answer: 4

<< shifts the bits left, and each place shifted left doubles the value:

\[ 2 = 10_2 \;\rightarrow\; 100_2 = 4 \]

So x becomes 4. Shifting a small positive int left is well defined, so the result does not depend on the compiler or the machine.

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