06

Question 1

What should happen when reading or writing to a NULL pointer?

Answer 1

An immediate crash.

Question 2

Can you cast the NULL pointer to a different type?

Answer 2

Yes

Question 3

Using arrow notation, what is the equivalent of this line?

(*x).y

Answer 3

x->y

Question 4

Can pointers be cast from one type to another?

Answer 4

Yes

Question 5

What sort of data can a void* point to?

Answer 5

Anything. They are used as a pointer of variable type.

Question 6

Why are void pointers not particularly useful?

Answer 6

They cannot be dereferenced or incremented/decremented.

Question 7

How many nested pointers can you have? (i.e. a pointer to a pointer to a pointer….)

Answer 7

There is no limit.

Question 8

What does an int** hold?

Answer 8

The memory address of an integer pointer.

Question 9

Given the function:
int add_numbers(double d, float f)
How would you declare a pointer to that function?

Answer 9

int (*ptr) (double, float) = &add_numbers;

Question 10

How do you declare a pointer to a function?

Answer 10

type (*ptr) (args,…) = function

Where type is the function type, ptr is the name of the pointer and args are the function arguments.

Question 11

When assert(x) is called, what happens if x is false?

Answer 11

The program aborts and prints an error message.

Question 12

What happens on underflow/ overflow on unsigned types?

Answer 12

Modulo arithmetic is performed. The values will ‘wrap around’.

Question 13

What is the ‘&’ operator?

Answer 13

A bitwise ‘and’

Question 14

What is the ‘|’ operator?

Answer 14

A bitwise ‘inclusive or’

Question 15

What is the ‘^’ operator?

Answer 15

A bitwise ‘exclusive or’

Question 16

What is the ‘~’ operator?

Answer 16

A bitwise one’s complement.

Question 17

How would you use the bitwise & operator to get the least significant byte from an integer x?

Answer 17

x & 0xff

Question 18

What operation does the ‘<

Answer 18

An arithmetic left shift.

Question 19

What operation does the ‘»’ operator perform?

Answer 19

An arithmetic right shift.

Question 20

What will be the value of i after the following line?

i = 2 &laquo_space;1

Answer 20

4.

An arithmetic left shift by N bits is equivalent to a multiplication by 2^n.

Question 21

What will be the value of i after the following line?

i = 36&raquo_space; 2

Answer 21

9.

An arithmetic right shift by N bits is equivalent to a division by 2^n.

Question 22

What does the following line do?

n |= 1 &laquo_space;x

Answer 22

Sets the xth bit of n to 1.

Question 23

What does the following line do?

n &= ~(1 &laquo_space;x)

Answer 23

Sets the xth bit of n to 0.

Question 24

What does the following line do?

n ^= 1 &laquo_space;x

Answer 24

Toggles the xth bit of n.

Question 25

What does the following line do?

n & (1 &laquo_space;x)

Answer 25

Checks the xth bit of n.

If it was 0, then n will now equal 0. Otherwise, n will be greater than 0.