Week 7

Question 1

What do we use to reference memory in the heap?

Answer 1

Pointers

Question 2

Who assigns memory?

Answer 2

The operating system

Question 3

The OS gets memory back when the program ends, but what is good programming practice?

Answer 3

To return it yourself

Question 4

What do we call getting memory from the heap in C?

Answer 4

memory management.

Question 5

What do we need to include for memory management?

Answer 5

stdlib.h

Question 6

How do we determine the number of bytes to request?

Answer 6

sizeof() function

Question 7

C lets you use a pointer as if it was an array. How do we access an element beyond where the pointer is pointing?

Answer 7

Using the […] notation to access elements beyonce where the pointer is pointing.

a_pointer[5] = 20;

Question 8

A common error with data structures and malloc is that the caller doesn’t allocate the space for the top structure. How do we write this properly?

Answer 8

bool stack_initialize(stack_t*the_stack){}
main() {
stack_t the_stack;
stack_initialize(&the_stack);
}

Question 9

A solution to the problem of a caller not allocating space is to do what?

Answer 9

Make the data structure responsible for all its space

Question 10

What is an alternative to malloc?

Answer 10

calloc

Question 11

Once allocated, does space in the heap change size?

Answer 11

Only if you ask it to change size

Question 12

After using realloc, any data in the previous space is copied into a new space. Are previous pointers into the old space still valid?

Answer 12

No, they’re no longer valid. You’re not guaranteed to get back a pointer to the same pace as before.

Question 13

How do we return space to the heap with a function?

Answer 13

void free(void *memory_to_return);

Question 14

What are the two main options for realloc?

Answer 14

Grow in place if possible

Copy to a new location if necessary

Question 15

Free does not clean up your pointer. How do we avoid mistakes?

Answer 15

Don’t keep using the pointer. You could be accessing memory that is given to another data structure!

Question 16

What do we do when we want dynamic arrays?

Answer 16

Use malloc or calloc

Track how full the array is

Use realloc to grow the array size when the array gets full

Question 17

What is a common trick to increasing the size of an array?

Answer 17

Start the array small and double its size each time that it needs to grow. At most half the array is empty after the first realloc

Question 18

What is a linked list?

Answer 18

A sequence of data values that are put together in a chain.

Question 19

What is a node?

Answer 19

One data value in the list

Question 20

Where does the last node in a linked list point?

Answer 20

null

Question 21

What do we include in the data type for a linked list node?

Answer 21

We use a struct to include both a value (an int or string) and a pointer

Question 22

What does the pointer in a node point to?

Answer 22

Another linked list node of the same data type

Question 23

how do we declare the pointer to a data type that we’re currently declaring?

Answer 23

Give the struct itself a name and use that name along with the struct keyword.