# GATE | GATE-CS-2003 | Question 90

`Consider the C program shown below.`

 `#include ` `#define print(x) printf("%d ", x) ` `int` `x; ` `void` `Q(``int` `z) ` `{ ` `    ``z += x; ` `    ``print(z); ` `} ` `void` `P(``int` `*y) ` `{ ` `    ``int` `x = *y + 2; ` `    ``Q(x); ` `    ``*y = x - 1; ` `    ``print(x); ` `} ` `main(``void``) ` `{ ` `    ``x = 5; ` `    ``P(&x); ` `    ``print(x); ` `}`

`The output of this program is`

(A) 12 7 6
(B) 22 12 11
(C) 14 6 6
(D) 7 6 6

Explanation: x is global so first x becomes 5 by the first line in main(). Then main() calls P() with address of x.

```// in main(void)

x = 5 // Change global x to 5
P(&x)
```

P() has a local variable named ‘x’ that hides global variable. P() theb calls Q() by passing value of local ‘x’.

```// In P(int *y)

int x = *y + 2; // Local x = 7
Q(x);
```

In Q(int z), z uses x which is global

```// In Q(int z)

z += x; // z becomes 5 + 7
printz(); // prints 12
```

After end of Q(), control comes back to P(). In P(), *y (y is address of global x) is changed to x – 1 (x is local to P()).

```// Back in P()

*y = x - 1; // *y = 7-1
print(x); // Prints 7
```

After end of Q(), control comes back to main(). In main(), global x is printed.

```// Back in main()

print(x); // prints 6 (updated in P()
//           by *y = x - 1 )
```
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