Data Storage and Representation

Study Notes

Data Storage

Data is stored in a computer system using binary code: 0s and 1s.
Each 0 or 1 is a bit. Groups of bits represent larger units of data.
Common units include:
- 1 byte = 8 bits
- 1 kilobyte (KB) = 1024 bytes
- 1 megabyte (MB) = 1024 kilobytes
- 1 gigabyte (GB) = 1024 megabytes
- 1 terabyte (TB) = 1024 gigabytes
Data is organized into files in a hierarchical file system. Files contain the data, and folders (directories) organize the files.
Different storage mediums exist:
- Primary storage (RAM): Volatile; contents lost when power is off; fast access speed; needed for currently running programs.
- Secondary storage (e.g., hard drives, SSDs): Non-volatile; contents are retained when power is off. Slower access speed than primary storage.

Data Representation

Text data is represented using character sets like ASCII or Unicode. Each character is assigned a unique binary code.
Images are represented using pixels with color values assigned to each in binary. Different image formats compress this data in various ways. Examples include JPEG and PNG.
Audio data is stored as a series of samples representing the sound waves. These samples are measured at a particular frequency (sample rate) and each sample is a binary value. Formats include MP3 or WAV.
Video: Video is a series of images (frames) displayed at a particular frame rate to create the illusion of movement. Each frame is represented using pixels, as is the case for images, and is therefore also stored and compressed as binary.
Numbers: Numbers are represented using different formats such as integers (positive and negative whole numbers) and floating-point numbers (numbers with decimal values).

Secondary Storage Devices

Hard Disk Drives (HDDs): Mechanical devices with spinning platters and read/write heads. Relatively cheap but slower than SSDs.
Solid State Drives (SSDs): Use flash memory chips; faster and more robust than HDDs. No moving parts. More expensive, but offer faster access speeds.
Optical Discs (CDs, DVDs, Blu-rays): Use lasers to read and write data, slower than HDDs and SSDs. Lower capacity typically.
USB Flash Drives: Portable storage devices using flash memory; fast and portable but limited capacity.

Data Compression

Compression techniques reduce the size of a file by removing redundant data or representing data more efficiently.
Lossless compression: Methods that allow the original data to be perfectly recovered. Examples include ZIP, RAR. No information is lost.
Lossy compression: Methods that discard some data during compression. Results in a smaller file size but a loss of quality. Examples include JPEG, MP3. Sometimes imperceptible differences in quality.

Factors Affecting Choice of Storage

Cost: HDDs are cheaper than SSDs; optical discs are even cheaper.
Speed: SSDs are faster than HDDs.
Capacity: HDDs typically have higher capacity than SSDs or USBs.
Portability: USBs and optical discs are highly portable.
Reliability: SSDs are more reliable than HDDs because they lack moving parts.

File Systems

File systems organize files and folders in storage devices. Important concepts include:
- Pathnames / file paths to provide the location of files on the disk.
- Directories / folders for organizing files.
- Metadata: data about the files stored, such as size, date created, last modified, etc.
File allocation tables track the storage locations of files on the disk.

Description

Explore the fundamentals of data storage and representation in computer systems. This quiz covers binary code, data units, file organization, and different storage mediums. Test your knowledge on how text and images are represented in digital formats.