SAM HARRIS TECH REVISION

1.2 Memory and Storage (OCR J277)

1.2.1 Primary Storage (Memory)

• RAM (Random Access Memory): Volatile memory that stores data and programs currently in use.
• ROM (Read Only Memory): Non-volatile memory containing the BIOS/boot-up instructions.
• Virtual Memory: A section of secondary storage used as RAM when RAM is full.

1.2.2 Secondary Storage

• The Need for Secondary Storage: Non-volatile storage for keeping programs and data indefinitely.
• Common Types: Optical (CD/DVD/Blu-ray), Magnetic (Hard Drive/Tape), and Solid State (SSD/USB Flash).
• Storage Characteristics: Comparing capacity, speed, portability, durability, reliability, and cost.

1.2.3 Units of Data Storage

• Units: Bit, nibble, byte, kilobyte, megabyte, gigabyte, terabyte, petabyte.
• Calculations: Converting between units and calculating data capacity requirements.

1.2.4 Data Representation

• Numbers: Binary, Denary, and Hexadecimal conversions; Binary addition and shifts.
• Characters: The use of binary codes (ASCII and Unicode) to represent characters.
• Images: Pixels, metadata, colour depth, and resolution.
• Sound: Sample rate, bit depth, and duration.

1.2.5 Compression

• Purpose: Reducing file size to save storage space or transmission time.
• Lossy vs Lossless: Understanding which method removes data and which preserves it perfectly.

Related Past Paper Questions

• Year: 2023 (June)
  The computer has Virtual Memory (VM). Describe how virtual memory is used when RAM is full.
  Mark: [4]
• Year: 2023 (June)
  A student has a text document and an image file that need to be compressed. Identify the most suitable type of compression for the text document and justify your choice.
  Mark: [3]
• Year: 2022 (June)
  Describe two differences between RAM and ROM.
  Mark: [4]
• Year: 2022 (June)
  A user is considering upgrading the RAM in their computer. Explain how this upgrade could improve the computer's performance.
  Mark: [2]
• Year: 2021 (November)
  Nina wants to transfer photos from a digital camera to an external secondary storage device. Identify the three common types of secondary storage Nina can choose from.
  Mark: [3]
• Year: 2021 (November)
  State four characteristics of secondary storage devices that should be considered when choosing a device for a specific purpose.
  Mark: [4]
• Year: 2020 (Sample Paper)
  Describe the purpose of ROM (Read Only Memory) in a tablet computer.
  Mark: [2]
• Year: 2020 (Sample Paper)
  Explain why a computer system needs secondary storage.
  Mark: [2]
• Year: 2023 (June)
  A digital image has a colour depth of 4 bits. State the maximum number of different colours that can be represented.
  Mark: [1]
• Year: 2022 (June)
  Identify one advantage and one disadvantage of using Magnetic storage compared to Solid State storage.
  Mark: [2]