1.2 Memory and storage

• Primary storage (primary memory)

  • A memory that CPU can directly access to, holds data and programs that are currently in use.
  • Very quick as it’s directly accessed by the CPU
  • Includes ROM and RAM
• RAM

  random access memory
• ROM

  read only memory
• RAM

  • volatile- all data is lost when computer turned off (temporar)
  • temporary storage of programs that are currently executing
  • can be written to and read from
• ROM

  • Non-volatile- data is permanent
  • Holds info such as BIOS ( Basic-Input- Output-System)- which is needed every time you open up the computer
  • Read only, can’t be written to
• Virtual memory

  • Used when there’s not enough storage in RAM from all the programs and data currently working on
  • Slower than secondary storage
• Secondary storage

  for long term storage and access of files and data because it’s non-volatile
• Secondary storage

  1. Magnetic
  2. Optical
  3. Solid state
• Magnetic storage device

  • hard disk drive
• Optical storage device

  • CD
  • BLU-RAY
• Solid state storage device

  • SSD
  • USB Stick
• Magnetic

  advantages:

  • high data capacity
  • durable and portable
  • cheap
• Magnetic

  Disadvantage:

  • has moving parts, vulnerable to fails
  • slower access speed
• Optical

  advantages

  • lightweight
  • portable - thin
  • cheap
• Optical

  disadvantage:

  • not durable- can loose data if surface scratched
  • low capacity
  • slowest
• Solid state

  advantage:

  • require very little power
  • portable- small in size
  • durable
  • very fast
• Solid state

  disadvantage:

  • small capacity
  • expensive
• what is bit?

  a single binary digit (1 or 0)
• what is nibble?


  4 bits ( 1001)
• How many bases are there in binary?


  2
• How many bases are there in denary?


  10 ( human only)
• What is hexadecimal?


  Base-16 number system. ( 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F,)
• why is hexadecimal used?

  • Efficiency and simplicity in representing binary data.
  • hex numbers are short so less chance of errors
  • Easier to convert between binary and hex values
• What is a character set?

  A collection of characters that a computer recognizes from their equivalent binary code
• What are the two types of character sets mentioned?

  • ASCII (American Standard Code for Information Interchange)
  • UNICODE
• What does ASCII stand for?

  American Standard Code for Information Interchange
• How many bits does ASCII use for each character?

  7 bits (8 bits for extended ASCII)
• How many different characters can ASCII represent?

  128 different characters
• What is the purpose of UNICODE?

  To cover every possible character or symbol and all major languages
• How many bits does UNICODE use for each character?

  16 bits
• How is the size of a text file calculated?

  File size (bits) = number of bits per character x number of characters
• What is metadata in an image file?

  Information stored in an image file, such as date, time, and resolution
• What is the purpose of metadata in an image file?

  To help the computer recreate the image on screen from binary data
• What are bitmap images made of?

  • Tiny squares called pixels
  • Each pixel's color is represented by a binary code
• How does the number of bits per pixel affect the number of colors in an image?

  The more bits per pixel, the more colors can be represented
• What is color depth?

  The number of bits used per pixel in an image
• How is the resolution of an image defined?

  By the number of pixels found in an image (length x width)
• How do you calculate the total number of colors in an image with color depth?

  Total number of colors = $2^n$ (where $n$ is the number of bits per pixel)
• What is the total number of colors in a 1-bit image?

  2 colors
• What is the total number of colors in a 4-bit image?

  16 colors