J277 Targeted Revision (Paper 1)

This session covers the exact gaps found in your AC1 assessment. It includes deep theory on CPU Architecture, Networks, and Legislation, followed by rigorous testing.

Instructions:
  • Read the theory sections carefully (click "Expand" for details).
  • Questions range from Foundation (Basic Recall) to Higher (Application).
  • If you get a question wrong, no answer is revealed. You must re-read the theory.

Topic 1: Systems Architecture

1.1 Von Neumann Architecture

Understanding the specific role of every register is critical. Don't just say "stores data".

▼ Expand Detailed Notes
  • PC (Program Counter): Stores the address of the next instruction to be fetched. It increments (+1) every cycle.
  • MAR (Memory Address Register): Stores the address of where data is being fetched from or written to.
  • MDR (Memory Data Register): Stores the actual data or instruction that has just been fetched from memory.
  • ACC (Accumulator): Stores the result of calculations from the ALU.
  • CU (Control Unit): Decodes instructions and sends control signals to coordinate data movement.

Exam Tip: Never confuse Address (MAR) with Data (MDR). Remember: A for Address, D for Data.

1.2 The Fetch-Execute Cycle

You must know the exact sequence of events.

▼ Expand Detailed Notes
  1. Fetch:
    • Address copied from PC to MAR.
    • Instruction fetched from RAM (at that address) to MDR.
    • PC is incremented (PC + 1) to point to the next instruction.
  2. Decode: The CU decodes the instruction in the MDR to understand what to do.
  3. Execute: The instruction is carried out (e.g., values loaded to ACC, or ALU performs calculation).

CPU Questions (Part 1/2)

Basic 1. Which register holds the address of the memory location currently being accessed?
Basic 2. The Program Counter (PC) stores the address of the ___________ instruction.
High Ability 3. In the Fetch-Execute cycle, what happens immediately after the address is copied to the MAR?
High Ability 4. Why does the PC increment (increase by 1) during the Fetch stage?

CPU Questions (Part 2/2)

Basic 5. Which component holds the result of a subtraction calculation?
High Ability 6. If the code `JUMP TO 50` is executed, which register is updated with the value 50?
High Ability 7. Which component is responsible for decoding instructions and synchronising the F-E cycle?

Topic 2: Networks & Connections

2.1 IP vs MAC Addresses

▼ Expand Detailed Notes
FeatureIP Address (v4)MAC Address
TypeLogical / ChangeablePhysical / Static (Hardware)
UsageRouting across WAN/InternetIdentification within LAN
Format4 denary numbers (0-255)
e.g., 192.168.1.1		12 Hex digits (6 pairs)
e.g., 1A:2B:3C:4D:5E:6F

IPv6: Created because IPv4 ran out of addresses. Uses 128-bits (8 groups of Hex). e.g., 2001:0db8:85a3::8a2e.

2.2 The DNS (Domain Name System)

You must describe the database lookup process.

▼ Expand Detailed Notes
  1. User types URL (domain name) into browser.
  2. Browser sends request to DNS Server.
  3. DNS Server checks its database to map the domain to an IP.
  4. If found, it returns the IP address to the browser.
  5. If not found, it passes the request to a higher-level DNS.
  6. Browser uses the IP to connect to the web server.

Networks Questions (Part 1/2)

Basic 8. Which device is required to connect a LAN to a WAN (like the Internet)?
High Ability 9. Which of the following is an INVALID IPv4 address? (Select one)
Basic 10. Which address is hard-wired into the network card by the manufacturer?
High Ability 11. In the DNS process, what happens immediately after the URL reaches the DNS server?

Networks Questions (Part 2/2)

High Ability 12. Why might a computer have a different IP address tomorrow, but the same MAC address?
Basic 13. IPv6 addresses are written using which number system?
High Ability 14. If a DNS server cannot find the IP address in its own database, what does it do?

Topic 3: Legislation & Licensing

3.1 UK Legislation Key Terms

Scenarios often trick you. Look for the "trigger" words.

▼ Expand Detailed Notes
  • Data Protection Act 2018 (DPA): Focuses on Personal Data. Triggers: Sharing address without consent, insecure storage, keeping data too long.
  • Computer Misuse Act 1990 (CMA): Focuses on Unauthorized Access. Triggers: Hacking, guessing passwords, installing malware/keyloggers.
  • Copyright Designs & Patents Act 1988 (CDPA): Focuses on Intellectual Property. Triggers: Copying images, piracy, stealing code.

3.2 Software Licensing

To get full marks on a recommendation, you must justify it.

▼ Expand Detailed Notes
  • Open Source: Source code is public. Users can edit/fix bugs. Usually free.
    Justification: "Choose this if you want the community to help fix bugs or if you have no budget."
  • Proprietary: Source code is closed. Users pay for a licence. Professional support.
    Justification: "Choose this if you want to sell the game for profit and protect your code from competitors."

Legislation Questions (Part 1/2)

Basic 15. A student guesses a teacher's password to log into their account. Which Act is broken?
Basic 16. A company sells client email addresses to a marketing firm without permission. Which Act is broken?
High Ability 17. A rival company copies the user interface code of your software exactly. Which Act protects you?
High Ability 18. What is the PRIMARY difference between Open Source and Proprietary licences?

Legislation Questions (Part 2/2)

High Ability 19. Scenario: A programmer wants to sell a game for profit and ensure nobody creates a "cheat" version by seeing the code. Which licence is best?
High Ability 20. Scenario: A charity wants a website but has no budget. They want volunteers to help improve the code. Which licence is best?
Basic 21. To comply with the DPA's requirement to keep data secure, what utility software should a youth centre use on their files?

Revision Complete

Well done, Student.

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