Assuming the compiler accepts the legacy C-style declarations shown below and…

2015

Assuming the compiler accepts the legacy C-style declarations shown below and printf is available, what does the following program print?

main()
{
inc(); inc(); inc();
}
inc()
{
static int x;
printf("%d", ++x);
}

Answer: B. prints 123 — ConceptA block-scope static variable has static storage duration: it is initialized only once, to zero when no initializer is supplied, and retains its stored…

  1. A.

    prints 012

  2. B.

    prints 123

  3. C.

    prints 3 consecutive, but unpredictable numbers

  4. D.

    prints 111

Attempted by 840 students.

Show answer & explanation

Correct answer: B

Concept

A block-scope static variable has static storage duration: it is initialized only once, to zero when no initializer is supplied, and retains its stored value across function calls. A prefix increment changes that stored value before the surrounding expression uses it.

Application

  1. Before the first call to inc(), the static variable x has its default initial value 0.

  2. On the first call, ++x changes x from 0 to 1, and printf displays 1.

  3. On the second call, x still stores 1; ++x changes it to 2, and printf displays 2.

  4. On the third call, x still stores 2; ++x changes it to 3, and printf displays 3.

Cross-check

The trace preserves x between calls and produces the sequence 1, 2, 3. The legacy-declaration assumption affects whether the source is accepted, not this state trace after acceptance.

Result

With the stated legacy-acceptance assumption, the program prints 123 without spaces.

Explore the full course: Iocl Engineers Officers Grade A Paper 2

Loading lesson…