Assume that the following C declarations are in effect: int a[4] = {6, 4, 1, 2};

Question

Assume that the following C declarations are in effect:

int a[4] = {6, 4, 1, 2};

int b[8] = {9, 8, 11, 10, 5, 7, 0, 3};

int *p = &a[1];

int *q = b;

int *r = b + 2;

Give the value of each of the following expressions. If an expression is illegal, give ILLEGAL as the answer. (Consider an expression to be illegal if it is rejected by a C compiler.) If an expression is legal but has an undefined value, give UNDEFINED as the answer.

(a) *p

(b) *q

(c) *r

(d) p + q

(e) r - q

(f) *(p + 1)

(g) q[3]

(h) b - a

Explanation / Answer

int a[4] = {6, 4, 1, 2};
int b[8] = {9, 8, 11, 10, 5, 7, 0, 3}; int *p = &a[1];
int *q = b;
int *r = b + 2;

a) *p => 4 => p pointing to second element of array a : a[1]
b) *q => 9 => q pointing to first element of array b: b[0], array name stores the address of first element
c) *r => 11 => r pointing to 3rd elemet of array b: r = b + 2 > adding 2 in base address
d) p + q => Illegal: invalid operands to binary expression ('int *' and 'int *')
e) r - q => 2 : number of blocks between r and q
f) *(p + 1) => 1 =>adding one in pointer points to next element, previously it was pointing to second element of a, now

it point to third element of array a
g) q[3] => 10 => q is pointing first element of b , now adding 3 in it, it points 4th element of b: q[3] = *(q+3)
h) b - a => // UNDEFINED

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