In-Depth Computer Science Notes for IB Exam

Computer Architecture

CPU Components:

• ALU: Performs arithmetic and logical operations.

• CU: Directs CPU operations.

• Registers: Fast storage for temporary data.

Memory Types:

• Primary Memory:

  • RAM: Volatile memory.

  • ROM: Non-volatile firmware.

  • Cache: High-speed data access.

Instruction Cycle:

• Fetch: Retrieve instruction.

• Decode: Process instruction.

• Execute: Perform the operation.

Storage Types

• Secondary Memory: Persistent data storage.

Operating Systems

• Functions: Manage hardware, provide user interface, execute tasks.

Application Software

• Designed for specific user tasks (e.g., word processing).

Binary Representation

• Key Terms:

  • Bit: Smallest data unit.

  • Byte: 8 bits.

  • Binary: Base-2 system.

  • Decimal: Base-10 system.

  • Hexadecimal: Base-16 system.

Data Representation:

• Data converted into binary for processing.

Logic Gates

• 
  

• Basic Gates:

  • AND: True when both inputs are true.

  • OR: True if at least one input is true.

  • NOT: Inverts input.

• 
  

• Truth Tables:

  
  

  • 
    

  • AND:
    

    A	B	A AND B
    0	0	0
    0	1	0
    1	0	0
    1	1	1
    OR:
    A	B	A OR B
    ---	---	--------
    0	0	0
    0	1	1
    1	0	1
    1	1	1
    NOT:
    A	NOT A
    ---	--------
    0	1
    1	0
    Advanced Gates:

    • NAND: Inverts AND output.

    • NOR: Inverts OR output.

    • XOR: True if inputs differ.

    Exam Preparation Notes

    • IB Symbols: Familiarize with specific logic gate symbols for IB exams.

    Combining Gates Examples:

    • Q = NOT (A AND B)

    • Q = NOT A NOR B

    • Q = C AND (A OR B)

    Practical Applications of Logic Gates:

    • AND: Smoke AND heat condition (fire alarm).

    • OR: Internal light IF door is open.

    • NOT: Microwave halts if door open.

    • NAND: Security systems engage without valid ID/code.

    • NOR: AC activates if all windows closed.

    • XOR: Two switches control one light.