The rest of the chapter.

• I want to cover 1.9 briefly
• Please read everything else.
• What is a linked list (list)
  • What is a doubly linked list?
  • What is a circularly linked list?
  • Check out klist.h in the kernel
• What is a stack?
• What is a queue?
• Check out kfifo.h.
• A tree
  • Is a data structure where
    • Data has a parent/child relationship
    • Exactly one node, the root, has no parent
    • Every other node has exactly one parent.
  • A binary tree is a special case of a tree where each node has at most two children.
  • A binary search tree is a binary tree with the special property that any value less than (or equal to) the value in a node is stored in the left sub-tre and any value greater is stored in the right sub-tree.
    • This is used for quick data recovery
    • Searching is O(n) for the degenerate case
    • But O(log₂(n)) for the best case.
  • A red black tree is a binary tree with additional restrictions to keep it balanced.
    • Really cool data structure
    • Insert and delete routines require rebalancing when the tree becomes unbalanced.
    • Which can be done quickly (O(log₂(n)) on average
  • A map/dictionary/hash table is an array that can be indexed with any arbitrary index.
    • Not just 0..n, where n is the size of the array.
    • It employs a hash function to map the index to the above range.
    • And ideally has access time O(1)
• These are all high level.
• bitmaps are low level.
  • Consider the system call open
  • open
  • This opens a file.
  • One of the parameters is for file permissions
    • rwx/ugo - 9 individual values.
    • Plus three special bits.
    • Way too many parameters.
  • But in 12 bits, we can represent all 2¹² combinations.
  • S_IXOTH
    • Give execute permission to others.
    • This is 00001₈
  • S_IWOTH is 00002₈
  • Take a look at bit.cpp.