Computer Science BS Journal (CST334) : Week 7

  This week in CST334 our lectures covered: IO Devices, Hard Drives, Files and Directories, File Systems(Data), and File Systems(Access). In this learning journal I'll write and explanation/what I think to be the most important bits of each subject. 

1. I/O Devices

I/O (Input/Output) devices are hardware that allow a computer to communicate with the outside world — keyboards, displays, printers, network cards, sensors, etc. They operate via controllers that communicate with the CPU and memory.

Key Takeaways:

  • Two main types: block devices (e.g., disks) and character devices (e.g., keyboards).

  • Managed through device drivers.

  • Performance depends on throughput (data per second) and latency (time per operation).

  • Communication methods: polling, interrupts, DMA (Direct Memory Access).

2. Hard Drives

Hard Disk Drives (HDDs) store data magnetically on spinning platters. Data is read/written by a moving read/write head.

Key Takeaways:

  • Performance factors: seek time, rotational latency, transfer rate.

  • Organized into tracks, sectors, and cylinders.

  • Sequential reads/writes are much faster than random access.

  • HDDs are non-volatile but slower than SSDs (solid-state drives).

3. Files and Directories

Files store data; directories organize files into a hierarchy. The OS manages these structures for storage and retrieval.

Key Takeaways:

  • Files have metadata (size, permissions, timestamps) and data.

  • Directories map names to file metadata (inode in Unix-like systems).

  • Paths can be absolute or relative.

  • Provides a logical view over physical storage.

4. File Systems (Data)

This refers to how file data and metadata are stored on disk — the on-disk structures that organize and manage storage space.

Key Takeaways:

  • Structures: superblock, inodes, data blocks, free space lists/bitmaps.

  • Must handle allocation, free space tracking, and crash recovery.

  • Examples: FAT32, NTFS, ext4.

  • Balances performance, space efficiency, and reliability.

5. File Systems (Access)

This is the interface the OS provides to programs for interacting with files and directories.

Key Takeaways:

  • Common API calls: open(), read(), write(), close(), mkdir(), unlink().

  • Supports permissions and access control.

  • May include caching and buffering for performance.

  • Virtual File System (VFS) layer abstracts different file system types.

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