Data structures play a big role in how much memory we use when we write computer programs. Here are some important points to understand:

1. Arrays:

   • Arrays have a set size, which means they use memory based on the number of items, noted as $O(n)$.
   • They store this memory all together, making it quick to access the items, with a time of $O(1)$.

2. Lists:

   • Lists can change size, so they also use $O(n)$ memory.
   • However, they use a bit more memory for pointers, which help keep track of where things are stored. Each pointer typically takes about $8$ bytes.
   • Because the items might not be stored next to each other, it can take longer to find what you need, average time being $O(n)$.

In general, data shows that arrays are usually better at saving memory than linked lists. Linked lists can use up to $25\%$ more memory because of those extra pointers.