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Operating systems

Free Files and disks lessons

7 lessons, about 1½ hours in all. Each teaches one idea with a visual, then gives you a problem or a few questions on it. Read the lessons here, then create a free account to practise and keep your progress.

Start free with lesson 1See the full Files and disks path

Stage 0Files

  1. Files and directoriesSee what a file is to the OS, how directories turn names into files, and what opening a path really does.12 min
  2. How file blocks are laid outCompare contiguous, linked and indexed allocation, and what each wastes.13 min
  3. InodesSee how a Unix file's record holds direct and indirect pointers, and work out the largest file it can describe.14 min
  4. Free space and crash safetySee how the OS tracks free blocks, and how a journal keeps the file system consistent after a crash.13 min

Stage 1Disks

  1. How long a disk access takesBreak a hard-disk read into seek, rotation and transfer, and see why positioning dominates small reads.12 min
  2. Disk schedulingOrder a queue of requests to cut head movement: FCFS, SSTF, SCAN, C-SCAN and LOOK.15 min

Stage 2Reliability

  1. RAIDCombine several disks for speed and survival: striping, mirroring and parity, and what each costs.13 min

All of Files and disks is free

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