1.2

1.2

1. 1.2.1

   • Primary storage is needed to hold both data and programs that are in current use by the CPU
   • RAM and ROM
     • RAM is Random Access Memory
       • It's volatile and holds any open documents and programs that are running
     • ROM is Read-Only Memory
       • It's non-volatile and holds instructions and data that are needed for the computer to run, like BIOS (Basic Input Output System)
   • Virtual Memory is the use of secondary storage as additional primary memory
     • This is when part of the computer's secondary storage can be used to store data temporarily.
       • Swapping is when the unused data in RAM is moved to virtual memory, and when it's needed, other unused data is moved to VM and the original data is moved back to RAM

2. 1.2.2

   • Secondary storage is needed to keep programs and data indefinitely
     • Types of secondary storage
       • Magnetic, e.g. hard disk drives
         • Cheapest, highest capacity, average speed, not portable, not very durable, quite reliable
       • Optical, e.g. CD, DVD, Blu-ray
         • Slowest, below average cost, lowest capacity, quite portable, not very durable, not very reliable
       • Solid state, e.g. USB drives
         • Priciest, fastest, average capacity, very portable, quite durable and reliable

3. 1.2.3

   • Units of data storage
     • Bit Nibble Byte Kilobyte Megabyte Gigabyte Terabyte Petabyte
     • ⬇ ⬇ ⬇ ⬇ ⬇ ⬇ ⬇ ⬇

4. 1.2.4

   • Numbers
     • 11100010 = E2 = 228
   • Characters
     • CHARACTER SET - All of the characters that a computer can use
   • Images
     • Images are a series of pixels (picture elements) represented in binary
       • Metadata; height and width of the image, the resolution, the colour depth
         • Colour depth is the number of bits used to store each pixel
           • Resolution is how many pixels are in the whole image (height x width)
   • Sound
     • The amplitude of the sound wave is sampled at regular intervals, and recorded as a binary value
       • Higher sample rate - better quality, larger file size
         • Longer duration - larger file size
           • Higher bit depth - larger file size
     • Bit depth is the number of bits used to record each sample
     • Bit rate is a measure of how much data is processed for each second of sound.

5. 1.2.5

   • Compression is needed to reduce file size for storage or transfer
     • Lossy is where data is lost permanently, but the size loss is more. Suitable for sound and image files
     • Lossless is where no data is lost but the size loss is less. Suitable for text files and software