Unit 1.3 Storage

Unit 1.3 Storage

1. Characteristics of storage devices

   • Capacity
   • Speed
   • Portability
   • Durabilty
   • Cost
   • Reliabilty

2. Data Capacity

   • Sound
     • bytesPerSample * samplesPerSecond * channels * duration = size
   • Images
     • (Number of pixels * Number of bytes per pixel) + 10% for any overheads
   • Text Files
     • 1 byte per character + 10% for any overheads

3. Storage Units

   • Past a byte tradititonally they go up x1,024 each time but in exams just use x1,000
   • Bits (1 or 0), Smallest
   • Nibble, 4 bits
   • Byte, 8 bits
   • Kilobyte (KB), 1,000 bytes
   • Megabyte (MB), 1,000 KB
   • Gigabyte (GB), 1,000 MB
   • Terabyte (TB), 1,000 GB
   • Pettabyte (PB), 1,000 TB

4. Data Types

   • Text = 1B/character
   • Integer = 4/8B
   • Real = 4/8B
   • Boolean = 1B
   • Date = 8B

5. Forms of Storage

   • Magnetic
     • Read/write makes certain parts more/less magnetised
     • How magnetised each part is represents a 1 or 0
   • Optical
     • A laser light leaves markings on a disk
     • Another laser scans these and makes them into a readable format
   • Solid State
     • Made of microchips
     • The state of each chip represents a 1 or 0
   • Secondary
     • We need this storage to save data ready for future use
     • We need it to interact with computers
     • It lets us use software
     • It is needed for a larger storage capacity and to back up data